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People should be able to +write Go programs and expect that they will continue to compile and run without +change, on a time scale of years, including in production environments such as +Google App Engine. Similarly, people should be able to write books about Go, be +able to say which version of Go the book is describing, and have that version +number still be meaningful much later. +</p> + +<p> +Code that compiles in Go 1 should, with few exceptions, continue to compile and +run throughout the lifetime of that version, even as we issue updates and bug +fixes such as Go version 1.1, 1.2, and so on. Other than critical fixes, changes +made to the language and library for subsequent releases of Go 1 may +add functionality but will not break existing Go 1 programs. +<a href="go1compat.html">The Go 1 compatibility document</a> +explains the compatibility guidelines in more detail. +</p> + +<p> +Go 1 is a representation of Go as it used today, not a wholesale rethinking of +the language. We avoided designing new features and instead focused on cleaning +up problems and inconsistencies and improving portability. There are a number +changes to the Go language and packages that we had considered for some time and +prototyped but not released primarily because they are significant and +backwards-incompatible. Go 1 was an opportunity to get them out, which is +helpful for the long term, but also means that Go 1 introduces incompatibilities +for old programs. Fortunately, the <code>go</code> <code>fix</code> tool can +automate much of the work needed to bring programs up to the Go 1 standard. +</p> + +<p> +This document outlines the major changes in Go 1 that will affect programmers +updating existing code; its reference point is the prior release, r60 (tagged as +r60.3). It also explains how to update code from r60 to run under Go 1. +</p> + +<h2 id="language">Changes to the language</h2> + +<h3 id="append">Append</h3> + +<p> +The <code>append</code> predeclared variadic function makes it easy to grow a slice +by adding elements to the end. +A common use is to add bytes to the end of a byte slice when generating output. +However, <code>append</code> did not provide a way to append a string to a <code>[]byte</code>, +which is another common case. +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/greeting := ..byte/` `/append.*hello/`}} +--> greeting := []byte{} + greeting = append(greeting, []byte("hello ")...)</pre> + +<p> +By analogy with the similar property of <code>copy</code>, Go 1 +permits a string to be appended (byte-wise) directly to a byte +slice, reducing the friction between strings and byte slices. +The conversion is no longer necessary: +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/append.*world/`}} +--> greeting = append(greeting, "world"...)</pre> + +<p> +<em>Updating</em>: +This is a new feature, so existing code needs no changes. +</p> + +<h3 id="close">Close</h3> + +<p> +The <code>close</code> predeclared function provides a mechanism +for a sender to signal that no more values will be sent. +It is important to the implementation of <code>for</code> <code>range</code> +loops over channels and is helpful in other situations. +Partly by design and partly because of race conditions that can occur otherwise, +it is intended for use only by the goroutine sending on the channel, +not by the goroutine receiving data. +However, before Go 1 there was no compile-time checking that <code>close</code> +was being used correctly. +</p> + +<p> +To close this gap, at least in part, Go 1 disallows <code>close</code> on receive-only channels. +Attempting to close such a channel is a compile-time error. +</p> + +<pre> + var c chan int + var csend chan<- int = c + var crecv <-chan int = c + close(c) // legal + close(csend) // legal + close(crecv) // illegal +</pre> + +<p> +<em>Updating</em>: +Existing code that attempts to close a receive-only channel was +erroneous even before Go 1 and should be fixed. The compiler will +now reject such code. +</p> + +<h3 id="literals">Composite literals</h3> + +<p> +In Go 1, a composite literal of array, slice, or map type can elide the +type specification for the elements' initializers if they are of pointer type. +All four of the initializations in this example are legal; the last one was illegal before Go 1. +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/type Date struct/` `/STOP/`}} +--> type Date struct { + month string + day int + } + <span class="comment">// Struct values, fully qualified; always legal.</span> + holiday1 := []Date{ + Date{"Feb", 14}, + Date{"Nov", 11}, + Date{"Dec", 25}, + } + <span class="comment">// Struct values, type name elided; always legal.</span> + holiday2 := []Date{ + {"Feb", 14}, + {"Nov", 11}, + {"Dec", 25}, + } + <span class="comment">// Pointers, fully qualified, always legal.</span> + holiday3 := []*Date{ + &Date{"Feb", 14}, + &Date{"Nov", 11}, + &Date{"Dec", 25}, + } + <span class="comment">// Pointers, type name elided; legal in Go 1.</span> + holiday4 := []*Date{ + {"Feb", 14}, + {"Nov", 11}, + {"Dec", 25}, + }</pre> + +<p> +<em>Updating</em>: +This change has no effect on existing code, but the command +<code>gofmt</code> <code>-s</code> applied to existing source +will, among other things, elide explicit element types wherever permitted. +</p> + + +<h3 id="init">Goroutines during init</h3> + +<p> +The old language defined that <code>go</code> statements executed during initialization created goroutines but that they did not begin to run until initialization of the entire program was complete. +This introduced clumsiness in many places and, in effect, limited the utility +of the <code>init</code> construct: +if it was possible for another package to use the library during initialization, the library +was forced to avoid goroutines. +This design was done for reasons of simplicity and safety but, +as our confidence in the language grew, it seemed unnecessary. +Running goroutines during initialization is no more complex or unsafe than running them during normal execution. +</p> + +<p> +In Go 1, code that uses goroutines can be called from +<code>init</code> routines and global initialization expressions +without introducing a deadlock. +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/PackageGlobal/` `/^}/`}} +-->var PackageGlobal int + +func init() { + c := make(chan int) + go initializationFunction(c) + PackageGlobal = <-c +}</pre> + +<p> +<em>Updating</em>: +This is a new feature, so existing code needs no changes, +although it's possible that code that depends on goroutines not starting before <code>main</code> will break. +There was no such code in the standard repository. +</p> + +<h3 id="rune">The rune type</h3> + +<p> +The language spec allows the <code>int</code> type to be 32 or 64 bits wide, but current implementations set <code>int</code> to 32 bits even on 64-bit platforms. +It would be preferable to have <code>int</code> be 64 bits on 64-bit platforms. +(There are important consequences for indexing large slices.) +However, this change would waste space when processing Unicode characters with +the old language because the <code>int</code> type was also used to hold Unicode code points: each code point would waste an extra 32 bits of storage if <code>int</code> grew from 32 bits to 64. +</p> + +<p> +To make changing to 64-bit <code>int</code> feasible, +Go 1 introduces a new basic type, <code>rune</code>, to represent +individual Unicode code points. +It is an alias for <code>int32</code>, analogous to <code>byte</code> +as an alias for <code>uint8</code>. +</p> + +<p> +Character literals such as <code>'a'</code>, <code>'語'</code>, and <code>'\u0345'</code> +now have default type <code>rune</code>, +analogous to <code>1.0</code> having default type <code>float64</code>. +A variable initialized to a character constant will therefore +have type <code>rune</code> unless otherwise specified. +</p> + +<p> +Libraries have been updated to use <code>rune</code> rather than <code>int</code> +when appropriate. For instance, the functions <code>unicode.ToLower</code> and +relatives now take and return a <code>rune</code>. +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/STARTRUNE/` `/ENDRUNE/`}} +--> delta := 'δ' <span class="comment">// delta has type rune.</span> + var DELTA rune + DELTA = unicode.ToUpper(delta) + epsilon := unicode.ToLower(DELTA + 1) + if epsilon != 'δ'+1 { + log.Fatal("inconsistent casing for Greek") + }</pre> + +<p> +<em>Updating</em>: +Most source code will be unaffected by this because the type inference from +<code>:=</code> initializers introduces the new type silently, and it propagates +from there. +Some code may get type errors that a trivial conversion will resolve. +</p> + +<h3 id="error">The error type</h3> + +<p> +Go 1 introduces a new built-in type, <code>error</code>, which has the following definition: +</p> + +<pre> + type error interface { + Error() string + } +</pre> + +<p> +Since the consequences of this type are all in the package library, +it is discussed <a href="#errors">below</a>. +</p> + +<h3 id="delete">Deleting from maps</h3> + +<p> +In the old language, to delete the entry with key <code>k</code> from map <code>m</code>, one wrote the statement, +</p> + +<pre> + m[k] = value, false +</pre> + +<p> +This syntax was a peculiar special case, the only two-to-one assignment. +It required passing a value (usually ignored) that is evaluated but discarded, +plus a boolean that was nearly always the constant <code>false</code>. +It did the job but was odd and a point of contention. +</p> + +<p> +In Go 1, that syntax has gone; instead there is a new built-in +function, <code>delete</code>. The call +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/delete\(m, k\)/`}} +--> delete(m, k)</pre> + +<p> +will delete the map entry retrieved by the expression <code>m[k]</code>. +There is no return value. Deleting a non-existent entry is a no-op. +</p> + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will convert expressions of the form <code>m[k] = value, +false</code> into <code>delete(m, k)</code> when it is clear that +the ignored value can be safely discarded from the program and +<code>false</code> refers to the predefined boolean constant. +The fix tool +will flag other uses of the syntax for inspection by the programmer. +</p> + +<h3 id="iteration">Iterating in maps</h3> + +<p> +The old language specification did not define the order of iteration for maps, +and in practice it differed across hardware platforms. +This caused tests that iterated over maps to be fragile and non-portable, with the +unpleasant property that a test might always pass on one machine but break on another. +</p> + +<p> +In Go 1, the order in which elements are visited when iterating +over a map using a <code>for</code> <code>range</code> statement +is defined to be unpredictable, even if the same loop is run multiple +times with the same map. +Code should not assume that the elements are visited in any particular order. +</p> + +<p> +This change means that code that depends on iteration order is very likely to break early and be fixed long before it becomes a problem. +Just as important, it allows the map implementation to ensure better map balancing even when programs are using range loops to select an element from a map. +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/Sunday/` `/^ }/`}} +--> m := map[string]int{"Sunday": 0, "Monday": 1} + for name, value := range m { + <span class="comment">// This loop should not assume Sunday will be visited first.</span> + f(name, value) + }</pre> + +<p> +<em>Updating</em>: +This is one change where tools cannot help. Most existing code +will be unaffected, but some programs may break or misbehave; we +recommend manual checking of all range statements over maps to +verify they do not depend on iteration order. There were a few such +examples in the standard repository; they have been fixed. +Note that it was already incorrect to depend on the iteration order, which +was unspecified. This change codifies the unpredictability. +</p> + +<h3 id="multiple_assignment">Multiple assignment</h3> + +<p> +The language specification has long guaranteed that in assignments +the right-hand-side expressions are all evaluated before any left-hand-side expressions are assigned. +To guarantee predictable behavior, +Go 1 refines the specification further. +</p> + +<p> +If the left-hand side of the assignment +statement contains expressions that require evaluation, such as +function calls or array indexing operations, these will all be done +using the usual left-to-right rule before any variables are assigned +their value. Once everything is evaluated, the actual assignments +proceed in left-to-right order. +</p> + +<p> +These examples illustrate the behavior. +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/sa :=/` `/then sc.0. = 2/`}} +--> sa := []int{1, 2, 3} + i := 0 + i, sa[i] = 1, 2 <span class="comment">// sets i = 1, sa[0] = 2</span> + + sb := []int{1, 2, 3} + j := 0 + sb[j], j = 2, 1 <span class="comment">// sets sb[0] = 2, j = 1</span> + + sc := []int{1, 2, 3} + sc[0], sc[0] = 1, 2 <span class="comment">// sets sc[0] = 1, then sc[0] = 2 (so sc[0] = 2 at end)</span></pre> + +<p> +<em>Updating</em>: +This is one change where tools cannot help, but breakage is unlikely. +No code in the standard repository was broken by this change, and code +that depended on the previous unspecified behavior was already incorrect. +</p> + +<h3 id="shadowing">Returns and shadowed variables</h3> + +<p> +A common mistake is to use <code>return</code> (without arguments) after an assignment to a variable that has the same name as a result variable but is not the same variable. +This situation is called <em>shadowing</em>: the result variable has been shadowed by another variable with the same name declared in an inner scope. +</p> + +<p> +In functions with named return values, +the Go 1 compilers disallow return statements without arguments if any of the named return values is shadowed at the point of the return statement. +(It isn't part of the specification, because this is one area we are still exploring; +the situation is analogous to the compilers rejecting functions that do not end with an explicit return statement.) +</p> + +<p> +This function implicitly returns a shadowed return value and will be rejected by the compiler: +</p> + +<pre> + func Bug() (i, j, k int) { + for i = 0; i < 5; i++ { + for j := 0; j < 5; j++ { // Redeclares j. + k += i*j + if k > 100 { + return // Rejected: j is shadowed here. + } + } + } + return // OK: j is not shadowed here. + } +</pre> + +<p> +<em>Updating</em>: +Code that shadows return values in this way will be rejected by the compiler and will need to be fixed by hand. +The few cases that arose in the standard repository were mostly bugs. +</p> + +<h3 id="unexported">Copying structs with unexported fields</h3> + +<p> +The old language did not allow a package to make a copy of a struct value containing unexported fields belonging to a different package. +There was, however, a required exception for a method receiver; +also, the implementations of <code>copy</code> and <code>append</code> have never honored the restriction. +</p> + +<p> +Go 1 will allow packages to copy struct values containing unexported fields from other packages. +Besides resolving the inconsistency, +this change admits a new kind of API: a package can return an opaque value without resorting to a pointer or interface. +The new implementations of <code>time.Time</code> and +<code>reflect.Value</code> are examples of types taking advantage of this new property. +</p> + +<p> +As an example, if package <code>p</code> includes the definitions, +</p> + +<pre> + type Struct struct { + Public int + secret int + } + func NewStruct(a int) Struct { // Note: not a pointer. + return Struct{a, f(a)} + } + func (s Struct) String() string { + return fmt.Sprintf("{%d (secret %d)}", s.Public, s.secret) + } +</pre> + +<p> +a package that imports <code>p</code> can assign and copy values of type +<code>p.Struct</code> at will. +Behind the scenes the unexported fields will be assigned and copied just +as if they were exported, +but the client code will never be aware of them. The code +</p> + +<pre> + import "p" + + myStruct := p.NewStruct(23) + copyOfMyStruct := myStruct + fmt.Println(myStruct, copyOfMyStruct) +</pre> + +<p> +will show that the secret field of the struct has been copied to the new value. +</p> + +<p> +<em>Updating</em>: +This is a new feature, so existing code needs no changes. +</p> + +<h3 id="equality">Equality</h3> + +<p> +Before Go 1, the language did not define equality on struct and array values. +This meant, +among other things, that structs and arrays could not be used as map keys. +On the other hand, Go did define equality on function and map values. +Function equality was problematic in the presence of closures +(when are two closures equal?) +while map equality compared pointers, not the maps' content, which was usually +not what the user would want. +</p> + +<p> +Go 1 addressed these issues. +First, structs and arrays can be compared for equality and inequality +(<code>==</code> and <code>!=</code>), +and therefore be used as map keys, +provided they are composed from elements for which equality is also defined, +using element-wise comparison. +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/type Day struct/` `/Printf/`}} +--> type Day struct { + long string + short string + } + Christmas := Day{"Christmas", "XMas"} + Thanksgiving := Day{"Thanksgiving", "Turkey"} + holiday := map[Day]bool{ + Christmas: true, + Thanksgiving: true, + } + fmt.Printf("Christmas is a holiday: %t\n", holiday[Christmas])</pre> + +<p> +Second, Go 1 removes the definition of equality for function values, +except for comparison with <code>nil</code>. +Finally, map equality is gone too, also except for comparison with <code>nil</code>. +</p> + +<p> +Note that equality is still undefined for slices, for which the +calculation is in general infeasible. Also note that the ordered +comparison operators (<code><</code> <code><=</code> +<code>></code> <code>>=</code>) are still undefined for +structs and arrays. + +<p> +<em>Updating</em>: +Struct and array equality is a new feature, so existing code needs no changes. +Existing code that depends on function or map equality will be +rejected by the compiler and will need to be fixed by hand. +Few programs will be affected, but the fix may require some +redesign. +</p> + +<h2 id="packages">The package hierarchy</h2> + +<p> +Go 1 addresses many deficiencies in the old standard library and +cleans up a number of packages, making them more internally consistent +and portable. +</p> + +<p> +This section describes how the packages have been rearranged in Go 1. +Some have moved, some have been renamed, some have been deleted. +New packages are described in later sections. +</p> + +<h3 id="hierarchy">The package hierarchy</h3> + +<p> +Go 1 has a rearranged package hierarchy that groups related items +into subdirectories. For instance, <code>utf8</code> and +<code>utf16</code> now occupy subdirectories of <code>unicode</code>. +Also, <a href="#subrepo">some packages</a> have moved into +subrepositories of +<a href="http://code.google.com/p/go"><code>code.google.com/p/go</code></a> +while <a href="#deleted">others</a> have been deleted outright. +</p> + +<table class="codetable" frame="border" summary="Moved packages"> +<colgroup align="left" width="60%"></colgroup> +<colgroup align="left" width="40%"></colgroup> +<tr> +<th align="left">Old path</th> +<th align="left">New path</th> +</tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>asn1</td> <td>encoding/asn1</td></tr> +<tr><td>csv</td> <td>encoding/csv</td></tr> +<tr><td>gob</td> <td>encoding/gob</td></tr> +<tr><td>json</td> <td>encoding/json</td></tr> +<tr><td>xml</td> <td>encoding/xml</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>exp/template/html</td> <td>html/template</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>big</td> <td>math/big</td></tr> +<tr><td>cmath</td> <td>math/cmplx</td></tr> +<tr><td>rand</td> <td>math/rand</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>http</td> <td>net/http</td></tr> +<tr><td>http/cgi</td> <td>net/http/cgi</td></tr> +<tr><td>http/fcgi</td> <td>net/http/fcgi</td></tr> +<tr><td>http/httptest</td> <td>net/http/httptest</td></tr> +<tr><td>http/pprof</td> <td>net/http/pprof</td></tr> +<tr><td>mail</td> <td>net/mail</td></tr> +<tr><td>rpc</td> <td>net/rpc</td></tr> +<tr><td>rpc/jsonrpc</td> <td>net/rpc/jsonrpc</td></tr> +<tr><td>smtp</td> <td>net/smtp</td></tr> +<tr><td>url</td> <td>net/url</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>exec</td> <td>os/exec</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>scanner</td> <td>text/scanner</td></tr> +<tr><td>tabwriter</td> <td>text/tabwriter</td></tr> +<tr><td>template</td> <td>text/template</td></tr> +<tr><td>template/parse</td> <td>text/template/parse</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>utf8</td> <td>unicode/utf8</td></tr> +<tr><td>utf16</td> <td>unicode/utf16</td></tr> +</table> + +<p> +Note that the package names for the old <code>cmath</code> and +<code>exp/template/html</code> packages have changed to <code>cmplx</code> +and <code>template</code>. +</p> + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will update all imports and package renames for packages that +remain inside the standard repository. Programs that import packages +that are no longer in the standard repository will need to be edited +by hand. +</p> + +<h3 id="exp">The package tree exp</h3> + +<p> +Because they are not standardized, the packages under the <code>exp</code> directory will not be available in the +standard Go 1 release distributions, although they will be available in source code form +in <a href="http://code.google.com/p/go/">the repository</a> for +developers who wish to use them. +</p> + +<p> +Several packages have moved under <code>exp</code> at the time of Go 1's release: +</p> + +<ul> +<li><code>ebnf</code></li> +<li><code>html</code><sup>†</sup></li> +<li><code>go/types</code></li> +</ul> + +<p> +(<sup>†</sup>The <code>EscapeString</code> and <code>UnescapeString</code> types remain +in package <code>html</code>.) +</p> + +<p> +All these packages are available under the same names, with the prefix <code>exp/</code>: <code>exp/ebnf</code> etc. +</p> + +<p> +Also, the <code>utf8.String</code> type has been moved to its own package, <code>exp/utf8string</code>. +</p> + +<p> +Finally, the <code>gotype</code> command now resides in <code>exp/gotype</code>, while +<code>ebnflint</code> is now in <code>exp/ebnflint</code>. +If they are installed, they now reside in <code>$GOROOT/bin/tool</code>. +</p> + +<p> +<em>Updating</em>: +Code that uses packages in <code>exp</code> will need to be updated by hand, +or else compiled from an installation that has <code>exp</code> available. +The <code>go</code> <code>fix</code> tool or the compiler will complain about such uses. +</p> + +<h3 id="old">The package tree old</h3> + +<p> +Because they are deprecated, the packages under the <code>old</code> directory will not be available in the +standard Go 1 release distributions, although they will be available in source code form for +developers who wish to use them. +</p> + +<p> +The packages in their new locations are: +</p> + +<ul> +<li><code>old/netchan</code></li> +<li><code>old/regexp</code></li> +<li><code>old/template</code></li> +</ul> + +<p> +<em>Updating</em>: +Code that uses packages now in <code>old</code> will need to be updated by hand, +or else compiled from an installation that has <code>old</code> available. +The <code>go</code> <code>fix</code> tool will warn about such uses. +</p> + +<h3 id="deleted">Deleted packages</h3> + +<p> +Go 1 deletes several packages outright: +</p> + +<ul> +<li><code>container/vector</code></li> +<li><code>exp/datafmt</code></li> +<li><code>go/typechecker</code></li> +<li><code>try</code></li> +</ul> + +<p> +and also the command <code>gotry</code>. +</p> + +<p> +<em>Updating</em>: +Code that uses <code>container/vector</code> should be updated to use +slices directly. See +<a href="http://code.google.com/p/go-wiki/wiki/SliceTricks">the Go +Language Community Wiki</a> for some suggestions. +Code that uses the other packages (there should be almost zero) will need to be rethought. +</p> + +<h3 id="subrepo">Packages moving to subrepositories</h3> + +<p> +Go 1 has moved a number of packages into other repositories, usually sub-repositories of +<a href="http://code.google.com/p/go/">the main Go repository</a>. +This table lists the old and new import paths: + +<table class="codetable" frame="border" summary="Sub-repositories"> +<colgroup align="left" width="40%"></colgroup> +<colgroup align="left" width="60%"></colgroup> +<tr> +<th align="left">Old</th> +<th align="left">New</th> +</tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>crypto/bcrypt</td> <td>code.google.com/p/go.crypto/bcrypt</tr> +<tr><td>crypto/blowfish</td> <td>code.google.com/p/go.crypto/blowfish</tr> +<tr><td>crypto/cast5</td> <td>code.google.com/p/go.crypto/cast5</tr> +<tr><td>crypto/md4</td> <td>code.google.com/p/go.crypto/md4</tr> +<tr><td>crypto/ocsp</td> <td>code.google.com/p/go.crypto/ocsp</tr> +<tr><td>crypto/openpgp</td> <td>code.google.com/p/go.crypto/openpgp</tr> +<tr><td>crypto/openpgp/armor</td> <td>code.google.com/p/go.crypto/openpgp/armor</tr> +<tr><td>crypto/openpgp/elgamal</td> <td>code.google.com/p/go.crypto/openpgp/elgamal</tr> +<tr><td>crypto/openpgp/errors</td> <td>code.google.com/p/go.crypto/openpgp/errors</tr> +<tr><td>crypto/openpgp/packet</td> <td>code.google.com/p/go.crypto/openpgp/packet</tr> +<tr><td>crypto/openpgp/s2k</td> <td>code.google.com/p/go.crypto/openpgp/s2k</tr> +<tr><td>crypto/ripemd160</td> <td>code.google.com/p/go.crypto/ripemd160</tr> +<tr><td>crypto/twofish</td> <td>code.google.com/p/go.crypto/twofish</tr> +<tr><td>crypto/xtea</td> <td>code.google.com/p/go.crypto/xtea</tr> +<tr><td>exp/ssh</td> <td>code.google.com/p/go.crypto/ssh</tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>image/bmp</td> <td>code.google.com/p/go.image/bmp</tr> +<tr><td>image/tiff</td> <td>code.google.com/p/go.image/tiff</tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>net/dict</td> <td>code.google.com/p/go.net/dict</tr> +<tr><td>net/websocket</td> <td>code.google.com/p/go.net/websocket</tr> +<tr><td>exp/spdy</td> <td>code.google.com/p/go.net/spdy</tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>encoding/git85</td> <td>code.google.com/p/go.codereview/git85</tr> +<tr><td>patch</td> <td>code.google.com/p/go.codereview/patch</tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>exp/wingui</td> <td>code.google.com/p/gowingui</tr> +</table> + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will update imports of these packages to use the new import paths. +Installations that depend on these packages will need to install them using +a <code>go get</code> command. +</p> + +<h2 id="major">Major changes to the library</h2> + +<p> +This section describes significant changes to the core libraries, the ones that +affect the most programs. +</p> + +<h3 id="errors">The error type and errors package</h3> + +<p> +The placement of <code>os.Error</code> in package <code>os</code> is mostly historical: errors first came up when implementing package <code>os</code>, and they seemed system-related at the time. +Since then it has become clear that errors are more fundamental than the operating system. For example, it would be nice to use <code>Errors</code> in packages that <code>os</code> depends on, like <code>syscall</code>. +Also, having <code>Error</code> in <code>os</code> introduces many dependencies on <code>os</code> that would otherwise not exist. +</p> + +<p> +Go 1 solves these problems by introducing a built-in <code>error</code> interface type and a separate <code>errors</code> package (analogous to <code>bytes</code> and <code>strings</code>) that contains utility functions. +It replaces <code>os.NewError</code> with +<a href="/pkg/errors/#New"><code>errors.New</code></a>, +giving errors a more central place in the environment. +</p> + +<p> +So the widely-used <code>String</code> method does not cause accidental satisfaction +of the <code>error</code> interface, the <code>error</code> interface uses instead +the name <code>Error</code> for that method: +</p> + +<pre> + type error interface { + Error() string + } +</pre> + +<p> +The <code>fmt</code> library automatically invokes <code>Error</code>, as it already +does for <code>String</code>, for easy printing of error values. +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/START ERROR EXAMPLE/` `/END ERROR EXAMPLE/`}} +-->type SyntaxError struct { + File string + Line int + Message string +} + +func (se *SyntaxError) Error() string { + return fmt.Sprintf("%s:%d: %s", se.File, se.Line, se.Message) +}</pre> + +<p> +All standard packages have been updated to use the new interface; the old <code>os.Error</code> is gone. +</p> + +<p> +A new package, <a href="/pkg/errors/"><code>errors</code></a>, contains the function +</p> + +<pre> +func New(text string) error +</pre> + +<p> +to turn a string into an error. It replaces the old <code>os.NewError</code>. +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/ErrSyntax/`}} +--> var ErrSyntax = errors.New("syntax error")</pre> + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will update almost all code affected by the change. +Code that defines error types with a <code>String</code> method will need to be updated +by hand to rename the methods to <code>Error</code>. +</p> + +<h3 id="errno">System call errors</h3> + +<p> +The old <code>syscall</code> package, which predated <code>os.Error</code> +(and just about everything else), +returned errors as <code>int</code> values. +In turn, the <code>os</code> package forwarded many of these errors, such +as <code>EINVAL</code>, but using a different set of errors on each platform. +This behavior was unpleasant and unportable. +</p> + +<p> +In Go 1, the +<a href="/pkg/syscall/"><code>syscall</code></a> +package instead returns an <code>error</code> for system call errors. +On Unix, the implementation is done by a +<a href="/pkg/syscall/#Errno"><code>syscall.Errno</code></a> type +that satisfies <code>error</code> and replaces the old <code>os.Errno</code>. +</p> + +<p> +The changes affecting <code>os.EINVAL</code> and relatives are +described <a href="#os">elsewhere</a>. + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will update almost all code affected by the change. +Regardless, most code should use the <code>os</code> package +rather than <code>syscall</code> and so will be unaffected. +</p> + +<h3 id="time">Time</h3> + +<p> +Time is always a challenge to support well in a programming language. +The old Go <code>time</code> package had <code>int64</code> units, no +real type safety, +and no distinction between absolute times and durations. +</p> + +<p> +One of the most sweeping changes in the Go 1 library is therefore a +complete redesign of the +<a href="/pkg/time/"><code>time</code></a> package. +Instead of an integer number of nanoseconds as an <code>int64</code>, +and a separate <code>*time.Time</code> type to deal with human +units such as hours and years, +there are now two fundamental types: +<a href="/pkg/time/#Time"><code>time.Time</code></a> +(a value, so the <code>*</code> is gone), which represents a moment in time; +and <a href="/pkg/time/#Duration"><code>time.Duration</code></a>, +which represents an interval. +Both have nanosecond resolution. +A <code>Time</code> can represent any time into the ancient +past and remote future, while a <code>Duration</code> can +span plus or minus only about 290 years. +There are methods on these types, plus a number of helpful +predefined constant durations such as <code>time.Second</code>. +</p> + +<p> +Among the new methods are things like +<a href="/pkg/time/#Time.Add"><code>Time.Add</code></a>, +which adds a <code>Duration</code> to a <code>Time</code>, and +<a href="/pkg/time/#Time.Sub"><code>Time.Sub</code></a>, +which subtracts two <code>Times</code> to yield a <code>Duration</code>. +</p> + +<p> +The most important semantic change is that the Unix epoch (Jan 1, 1970) is now +relevant only for those functions and methods that mention Unix: +<a href="/pkg/time/#Unix"><code>time.Unix</code></a> +and the <a href="/pkg/time/#Time.Unix"><code>Unix</code></a> +and <a href="/pkg/time/#Time.UnixNano"><code>UnixNano</code></a> methods +of the <code>Time</code> type. +In particular, +<a href="/pkg/time/#Now"><code>time.Now</code></a> +returns a <code>time.Time</code> value rather than, in the old +API, an integer nanosecond count since the Unix epoch. +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/sleepUntil/` `/^}/`}} +--><span class="comment">// sleepUntil sleeps until the specified time. It returns immediately if it's too late.</span> +func sleepUntil(wakeup time.Time) { + now := time.Now() <span class="comment">// A Time.</span> + if !wakeup.After(now) { + return + } + delta := wakeup.Sub(now) <span class="comment">// A Duration.</span> + fmt.Printf("Sleeping for %.3fs\n", delta.Seconds()) + time.Sleep(delta) +}</pre> + +<p> +The new types, methods, and constants have been propagated through +all the standard packages that use time, such as <code>os</code> and +its representation of file time stamps. +</p> + +<p> +<em>Updating</em>: +The <code>go</code> <code>fix</code> tool will update many uses of the old <code>time</code> package to use the new +types and methods, although it does not replace values such as <code>1e9</code> +representing nanoseconds per second. +Also, because of type changes in some of the values that arise, +some of the expressions rewritten by the fix tool may require +further hand editing; in such cases the rewrite will include +the correct function or method for the old functionality, but +may have the wrong type or require further analysis. +</p> + +<h2 id="minor">Minor changes to the library</h2> + +<p> +This section describes smaller changes, such as those to less commonly +used packages or that affect +few programs beyond the need to run <code>go</code> <code>fix</code>. +This category includes packages that are new in Go 1. +Collectively they improve portability, regularize behavior, and +make the interfaces more modern and Go-like. +</p> + +<h3 id="archive_zip">The archive/zip package</h3> + +<p> +In Go 1, <a href="/pkg/archive/zip/#Writer"><code>*zip.Writer</code></a> no +longer has a <code>Write</code> method. Its presence was a mistake. +</p> + +<p> +<em>Updating</em>: +What little code is affected will be caught by the compiler and must be updated by hand. +</p> + +<h3 id="bufio">The bufio package</h3> + +<p> +In Go 1, <a href="/pkg/bufio/#NewReaderSize"><code>bufio.NewReaderSize</code></a> +and +<a href="/pkg/bufio/#NewWriterSize"><code>bufio.NewWriterSize</code></a> +functions no longer return an error for invalid sizes. +If the argument size is too small or invalid, it is adjusted. +</p> + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will update calls that assign the error to _. +Calls that aren't fixed will be caught by the compiler and must be updated by hand. +</p> + +<h3 id="compress">The compress/flate, compress/gzip and compress/zlib packages</h3> + +<p> +In Go 1, the <code>NewWriterXxx</code> functions in +<a href="/pkg/compress/flate"><code>compress/flate</code></a>, +<a href="/pkg/compress/gzip"><code>compress/gzip</code></a> and +<a href="/pkg/compress/zlib"><code>compress/zlib</code></a> +all return <code>(*Writer, error)</code> if they take a compression level, +and <code>*Writer</code> otherwise. Package <code>gzip</code>'s +<code>Compressor</code> and <code>Decompressor</code> types have been renamed +to <code>Writer</code> and <code>Reader</code>. Package <code>flate</code>'s +<code>WrongValueError</code> type has been removed. +</p> + +<p> +<em>Updating</em> +Running <code>go</code> <code>fix</code> will update old names and calls that assign the error to _. +Calls that aren't fixed will be caught by the compiler and must be updated by hand. +</p> + +<h3 id="crypto_aes_des">The crypto/aes and crypto/des packages</h3> + +<p> +In Go 1, the <code>Reset</code> method has been removed. Go does not guarantee +that memory is not copied and therefore this method was misleading. +</p> + +<p> +The cipher-specific types <code>*aes.Cipher</code>, <code>*des.Cipher</code>, +and <code>*des.TripleDESCipher</code> have been removed in favor of +<code>cipher.Block</code>. +</p> + +<p> +<em>Updating</em>: +Remove the calls to Reset. Replace uses of the specific cipher types with +cipher.Block. +</p> + +<h3 id="crypto_elliptic">The crypto/elliptic package</h3> + +<p> +In Go 1, <a href="/pkg/crypto/elliptic/#Curve"><code>elliptic.Curve</code></a> +has been made an interface to permit alternative implementations. The curve +parameters have been moved to the +<a href="/pkg/crypto/elliptic/#CurveParams"><code>elliptic.CurveParams</code></a> +structure. +</p> + +<p> +<em>Updating</em>: +Existing users of <code>*elliptic.Curve</code> will need to change to +simply <code>elliptic.Curve</code>. Calls to <code>Marshal</code>, +<code>Unmarshal</code> and <code>GenerateKey</code> are now functions +in <code>crypto/elliptic</code> that take an <code>elliptic.Curve</code> +as their first argument. +</p> + +<h3 id="crypto_hmac">The crypto/hmac package</h3> + +<p> +In Go 1, the hash-specific functions, such as <code>hmac.NewMD5</code>, have +been removed from <code>crypto/hmac</code>. Instead, <code>hmac.New</code> takes +a function that returns a <code>hash.Hash</code>, such as <code>md5.New</code>. +</p> + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will perform the needed changes. +</p> + +<h3 id="crypto_x509">The crypto/x509 package</h3> + +<p> +In Go 1, the +<a href="/pkg/crypto/x509/#CreateCertificate"><code>CreateCertificate</code></a> +and +<a href="/pkg/crypto/x509/#CreateCRL"><code>CreateCRL</code></a> +functions in <code>crypto/x509</code> have been altered to take an +<code>interface{}</code> where they previously took a <code>*rsa.PublicKey</code> +or <code>*rsa.PrivateKey</code>. This will allow other public key algorithms +to be implemented in the future. +</p> + +<p> +<em>Updating</em>: +No changes will be needed. +</p> + +<h3 id="encoding_binary">The encoding/binary package</h3> + +<p> +In Go 1, the <code>binary.TotalSize</code> function has been replaced by +<a href="/pkg/encoding/binary/#Size"><code>Size</code></a>, +which takes an <code>interface{}</code> argument rather than +a <code>reflect.Value</code>. +</p> + +<p> +<em>Updating</em>: +What little code is affected will be caught by the compiler and must be updated by hand. +</p> + +<h3 id="encoding_xml">The encoding/xml package</h3> + +<p> +In Go 1, the <a href="/pkg/encoding/xml/"><code>xml</code></a> package +has been brought closer in design to the other marshaling packages such +as <a href="/pkg/encoding/gob/"><code>encoding/gob</code></a>. +</p> + +<p> +The old <code>Parser</code> type is renamed +<a href="/pkg/encoding/xml/#Decoder"><code>Decoder</code></a> and has a new +<a href="/pkg/encoding/xml/#Decoder.Decode"><code>Decode</code></a> method. An +<a href="/pkg/encoding/xml/#Encoder"><code>Encoder</code></a> type was also introduced. +</p> + +<p> +The functions <a href="/pkg/encoding/xml/#Marshal"><code>Marshal</code></a> +and <a href="/pkg/encoding/xml/#Unmarshal"><code>Unmarshal</code></a> +work with <code>[]byte</code> values now. To work with streams, +use the new <a href="/pkg/encoding/xml/#Encoder"><code>Encoder</code></a> +and <a href="/pkg/encoding/xml/#Decoder"><code>Decoder</code></a> types. +</p> + +<p> +When marshaling or unmarshaling values, the format of supported flags in +field tags has changed to be closer to the +<a href="/pkg/encoding/json"><code>json</code></a> package +(<code>`xml:"name,flag"`</code>). The matching done between field tags, field +names, and the XML attribute and element names is now case-sensitive. +The <code>XMLName</code> field tag, if present, must also match the name +of the XML element being marshaled. +</p> + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will update most uses of the package except for some calls to +<code>Unmarshal</code>. Special care must be taken with field tags, +since the fix tool will not update them and if not fixed by hand they will +misbehave silently in some cases. For example, the old +<code>"attr"</code> is now written <code>",attr"</code> while plain +<code>"attr"</code> remains valid but with a different meaning. +</p> + +<h3 id="expvar">The expvar package</h3> + +<p> +In Go 1, the <code>RemoveAll</code> function has been removed. +The <code>Iter</code> function and Iter method on <code>*Map</code> have +been replaced by +<a href="/pkg/expvar/#Do"><code>Do</code></a> +and +<a href="/pkg/expvar/#Map.Do"><code>(*Map).Do</code></a>. +</p> + +<p> +<em>Updating</em>: +Most code using <code>expvar</code> will not need changing. The rare code that used +<code>Iter</code> can be updated to pass a closure to <code>Do</code> to achieve the same effect. +</p> + +<h3 id="flag">The flag package</h3> + +<p> +In Go 1, the interface <a href="/pkg/flag/#Value"><code>flag.Value</code></a> has changed slightly. +The <code>Set</code> method now returns an <code>error</code> instead of +a <code>bool</code> to indicate success or failure. +</p> + +<p> +There is also a new kind of flag, <code>Duration</code>, to support argument +values specifying time intervals. +Values for such flags must be given units, just as <code>time.Duration</code> +formats them: <code>10s</code>, <code>1h30m</code>, etc. +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/timeout/`}} +-->var timeout = flag.Duration("timeout", 30*time.Second, "how long to wait for completion")</pre> + +<p> +<em>Updating</em>: +Programs that implement their own flags will need minor manual fixes to update their +<code>Set</code> methods. +The <code>Duration</code> flag is new and affects no existing code. +</p> + + +<h3 id="go">The go/* packages</h3> + +<p> +Several packages under <code>go</code> have slightly revised APIs. +</p> + +<p> +A concrete <code>Mode</code> type was introduced for configuration mode flags +in the packages +<a href="/pkg/go/scanner/"><code>go/scanner</code></a>, +<a href="/pkg/go/parser/"><code>go/parser</code></a>, +<a href="/pkg/go/printer/"><code>go/printer</code></a>, and +<a href="/pkg/go/doc/"><code>go/doc</code></a>. +</p> + +<p> +The modes <code>AllowIllegalChars</code> and <code>InsertSemis</code> have been removed +from the <a href="/pkg/go/scanner/"><code>go/scanner</code></a> package. They were mostly +useful for scanning text other then Go source files. Instead, the +<a href="/pkg/text/scanner/"><code>text/scanner</code></a> package should be used +for that purpose. +</p> + +<p> +The <a href="/pkg/go/scanner/#ErrorHandler"><code>ErrorHandler</code></a> provided +to the scanner's <a href="/pkg/go/scanner/#Scanner.Init"><code>Init</code></a> method is +now simply a function rather than an interface. The <code>ErrorVector</code> type has +been removed in favor of the (existing) <a href="/pkg/go/scanner/#ErrorList"><code>ErrorList</code></a> +type, and the <code>ErrorVector</code> methods have been migrated. Instead of embedding +an <code>ErrorVector</code> in a client of the scanner, now a client should maintain +an <code>ErrorList</code>. +</p> + +<p> +The set of parse functions provided by the <a href="/pkg/go/parser/"><code>go/parser</code></a> +package has been reduced to the primary parse function +<a href="/pkg/go/parser/#ParseFile"><code>ParseFile</code></a>, and a couple of +convenience functions <a href="/pkg/go/parser/#ParseDir"><code>ParseDir</code></a> +and <a href="/pkg/go/parser/#ParseExpr"><code>ParseExpr</code></a>. +</p> + +<p> +The <a href="/pkg/go/printer/"><code>go/printer</code></a> package supports an additional +configuration mode <a href="/pkg/go/printer/#Mode"><code>SourcePos</code></a>; +if set, the printer will emit <code>//line</code> comments such that the generated +output contains the original source code position information. The new type +<a href="/pkg/go/printer/#CommentedNode"><code>CommentedNode</code></a> can be +used to provide comments associated with an arbitrary +<a href="/pkg/go/ast/#Node"><code>ast.Node</code></a> (until now only +<a href="/pkg/go/ast/#File"><code>ast.File</code></a> carried comment information). +</p> + +<p> +The type names of the <a href="/pkg/go/doc/"><code>go/doc</code></a> package have been +streamlined by removing the <code>Doc</code> suffix: <code>PackageDoc</code> +is now <code>Package</code>, <code>ValueDoc</code> is <code>Value</code>, etc. +Also, all types now consistently have a <code>Name</code> field (or <code>Names</code>, +in the case of type <code>Value</code>) and <code>Type.Factories</code> has become +<code>Type.Funcs</code>. +Instead of calling <code>doc.NewPackageDoc(pkg, importpath)</code>, +documentation for a package is created with: +</p> + +<pre> + doc.New(pkg, importpath, mode) +</pre> + +<p> +where the new <code>mode</code> parameter specifies the operation mode: +if set to <a href="/pkg/go/doc/#AllDecls"><code>AllDecls</code></a>, all declarations +(not just exported ones) are considered. +The function <code>NewFileDoc</code> was removed, and the function +<code>CommentText</code> has become the method +<a href="/pkg/go/ast/#Text"><code>Text</code></a> of +<a href="/pkg/go/ast/#CommentGroup"><code>ast.CommentGroup</code></a>. +</p> + +<p> +In package <a href="/pkg/go/token/"><code>go/token</code></a>, the +<a href="/pkg/go/token/#FileSet"><code>token.FileSet</code></a> method <code>Files</code> +(which originally returned a channel of <code>*token.File</code>s) has been replaced +with the iterator <a href="/pkg/go/token/#FileSet.Iterate"><code>Iterate</code></a> that +accepts a function argument instead. +</p> + +<p> +In package <a href="/pkg/go/build/"><code>go/build</code></a>, the API +has been nearly completely replaced. +The package still computes Go package information +but it does not run the build: the <code>Cmd</code> and <code>Script</code> +types are gone. +(To build code, use the new +<a href="/cmd/go/"><code>go</code></a> command instead.) +The <code>DirInfo</code> type is now named +<a href="/pkg/go/build/#Package"><code>Package</code></a>. +<code>FindTree</code> and <code>ScanDir</code> are replaced by +<a href="/pkg/go/build/#Import"><code>Import</code></a> +and +<a href="/pkg/go/build/#ImportDir"><code>ImportDir</code></a>. +</p> + +<p> +<em>Updating</em>: +Code that uses packages in <code>go</code> will have to be updated by hand; the +compiler will reject incorrect uses. Templates used in conjunction with any of the +<code>go/doc</code> types may need manual fixes; the renamed fields will lead +to run-time errors. +</p> + +<h3 id="hash">The hash package</h3> + +<p> +In Go 1, the definition of <a href="/pkg/hash/#Hash"><code>hash.Hash</code></a> includes +a new method, <code>BlockSize</code>. This new method is used primarily in the +cryptographic libraries. +</p> + +<p> +The <code>Sum</code> method of the +<a href="/pkg/hash/#Hash"><code>hash.Hash</code></a> interface now takes a +<code>[]byte</code> argument, to which the hash value will be appended. +The previous behavior can be recreated by adding a <code>nil</code> argument to the call. +</p> + +<p> +<em>Updating</em>: +Existing implementations of <code>hash.Hash</code> will need to add a +<code>BlockSize</code> method. Hashes that process the input one byte at +a time can implement <code>BlockSize</code> to return 1. +Running <code>go</code> <code>fix</code> will update calls to the <code>Sum</code> methods of the various +implementations of <code>hash.Hash</code>. +</p> + +<p> +<em>Updating</em>: +Since the package's functionality is new, no updating is necessary. +</p> + +<h3 id="http">The http package</h3> + +<p> +In Go 1 the <a href="/pkg/net/http/"><code>http</code></a> package is refactored, +putting some of the utilities into a +<a href="/pkg/net/http/httputil/"><code>httputil</code></a> subdirectory. +These pieces are only rarely needed by HTTP clients. +The affected items are: +</p> + +<ul> +<li>ClientConn</li> +<li>DumpRequest</li> +<li>DumpRequestOut</li> +<li>DumpResponse</li> +<li>NewChunkedReader</li> +<li>NewChunkedWriter</li> +<li>NewClientConn</li> +<li>NewProxyClientConn</li> +<li>NewServerConn</li> +<li>NewSingleHostReverseProxy</li> +<li>ReverseProxy</li> +<li>ServerConn</li> +</ul> + +<p> +The <code>Request.RawURL</code> field has been removed; it was a +historical artifact. +</p> + +<p> +The <code>Handle</code> and <code>HandleFunc</code> +functions, and the similarly-named methods of <code>ServeMux</code>, +now panic if an attempt is made to register the same pattern twice. +</p> + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will update the few programs that are affected except for +uses of <code>RawURL</code>, which must be fixed by hand. +</p> + +<h3 id="image">The image package</h3> + +<p> +The <a href="/pkg/image/"><code>image</code></a> package has had a number of +minor changes, rearrangements and renamings. +</p> + +<p> +Most of the color handling code has been moved into its own package, +<a href="/pkg/image/color/"><code>image/color</code></a>. +For the elements that moved, a symmetry arises; for instance, +each pixel of an +<a href="/pkg/image/#RGBA"><code>image.RGBA</code></a> +is a +<a href="/pkg/image/color/#RGBA"><code>color.RGBA</code></a>. +</p> + +<p> +The old <code>image/ycbcr</code> package has been folded, with some +renamings, into the +<a href="/pkg/image/"><code>image</code></a> +and +<a href="/pkg/image/color/"><code>image/color</code></a> +packages. +</p> + +<p> +The old <code>image.ColorImage</code> type is still in the <code>image</code> +package but has been renamed +<a href="/pkg/image/#Uniform"><code>image.Uniform</code></a>, +while <code>image.Tiled</code> has been removed. +</p> + +<p> +This table lists the renamings. +</p> + +<table class="codetable" frame="border" summary="image renames"> +<colgroup align="left" width="50%"></colgroup> +<colgroup align="left" width="50%"></colgroup> +<tr> +<th align="left">Old</th> +<th align="left">New</th> +</tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>image.Color</td> <td>color.Color</td></tr> +<tr><td>image.ColorModel</td> <td>color.Model</td></tr> +<tr><td>image.ColorModelFunc</td> <td>color.ModelFunc</td></tr> +<tr><td>image.PalettedColorModel</td> <td>color.Palette</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>image.RGBAColor</td> <td>color.RGBA</td></tr> +<tr><td>image.RGBA64Color</td> <td>color.RGBA64</td></tr> +<tr><td>image.NRGBAColor</td> <td>color.NRGBA</td></tr> +<tr><td>image.NRGBA64Color</td> <td>color.NRGBA64</td></tr> +<tr><td>image.AlphaColor</td> <td>color.Alpha</td></tr> +<tr><td>image.Alpha16Color</td> <td>color.Alpha16</td></tr> +<tr><td>image.GrayColor</td> <td>color.Gray</td></tr> +<tr><td>image.Gray16Color</td> <td>color.Gray16</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>image.RGBAColorModel</td> <td>color.RGBAModel</td></tr> +<tr><td>image.RGBA64ColorModel</td> <td>color.RGBA64Model</td></tr> +<tr><td>image.NRGBAColorModel</td> <td>color.NRGBAModel</td></tr> +<tr><td>image.NRGBA64ColorModel</td> <td>color.NRGBA64Model</td></tr> +<tr><td>image.AlphaColorModel</td> <td>color.AlphaModel</td></tr> +<tr><td>image.Alpha16ColorModel</td> <td>color.Alpha16Model</td></tr> +<tr><td>image.GrayColorModel</td> <td>color.GrayModel</td></tr> +<tr><td>image.Gray16ColorModel</td> <td>color.Gray16Model</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>ycbcr.RGBToYCbCr</td> <td>color.RGBToYCbCr</td></tr> +<tr><td>ycbcr.YCbCrToRGB</td> <td>color.YCbCrToRGB</td></tr> +<tr><td>ycbcr.YCbCrColorModel</td> <td>color.YCbCrModel</td></tr> +<tr><td>ycbcr.YCbCrColor</td> <td>color.YCbCr</td></tr> +<tr><td>ycbcr.YCbCr</td> <td>image.YCbCr</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>ycbcr.SubsampleRatio444</td> <td>image.YCbCrSubsampleRatio444</td></tr> +<tr><td>ycbcr.SubsampleRatio422</td> <td>image.YCbCrSubsampleRatio422</td></tr> +<tr><td>ycbcr.SubsampleRatio420</td> <td>image.YCbCrSubsampleRatio420</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>image.ColorImage</td> <td>image.Uniform</td></tr> +</table> + +<p> +The image package's <code>New</code> functions +(<a href="/pkg/image/#NewRGBA"><code>NewRGBA</code></a>, +<a href="/pkg/image/#NewRGBA64"><code>NewRGBA64</code></a>, etc.) +take an <a href="/pkg/image/#Rectangle"><code>image.Rectangle</code></a> as an argument +instead of four integers. +</p> + +<p> +Finally, there are new predefined <code>color.Color</code> variables +<a href="/pkg/image/color/#Black"><code>color.Black</code></a>, +<a href="/pkg/image/color/#White"><code>color.White</code></a>, +<a href="/pkg/image/color/#Opaque"><code>color.Opaque</code></a> +and +<a href="/pkg/image/color/#Transparent"><code>color.Transparent</code></a>. +</p> + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will update almost all code affected by the change. +</p> + +<h3 id="log_syslog">The log/syslog package</h3> + +<p> +In Go 1, the <a href="/pkg/log/syslog/#NewLogger"><code>syslog.NewLogger</code></a> +function returns an error as well as a <code>log.Logger</code>. +</p> + +<p> +<em>Updating</em>: +What little code is affected will be caught by the compiler and must be updated by hand. +</p> + +<h3 id="mime">The mime package</h3> + +<p> +In Go 1, the <a href="/pkg/mime/#FormatMediaType"><code>FormatMediaType</code></a> function +of the <code>mime</code> package has been simplified to make it +consistent with +<a href="/pkg/mime/#ParseMediaType"><code>ParseMediaType</code></a>. +It now takes <code>"text/html"</code> rather than <code>"text"</code> and <code>"html"</code>. +</p> + +<p> +<em>Updating</em>: +What little code is affected will be caught by the compiler and must be updated by hand. +</p> + +<h3 id="net">The net package</h3> + +<p> +In Go 1, the various <code>SetTimeout</code>, +<code>SetReadTimeout</code>, and <code>SetWriteTimeout</code> methods +have been replaced with +<a href="/pkg/net/#IPConn.SetDeadline"><code>SetDeadline</code></a>, +<a href="/pkg/net/#IPConn.SetReadDeadline"><code>SetReadDeadline</code></a>, and +<a href="/pkg/net/#IPConn.SetWriteDeadline"><code>SetWriteDeadline</code></a>, +respectively. Rather than taking a timeout value in nanoseconds that +apply to any activity on the connection, the new methods set an +absolute deadline (as a <code>time.Time</code> value) after which +reads and writes will time out and no longer block. +</p> + +<p> +There are also new functions +<a href="/pkg/net/#DialTimeout"><code>net.DialTimeout</code></a> +to simplify timing out dialing a network address and +<a href="/pkg/net/#ListenMulticastUDP"><code>net.ListenMulticastUDP</code></a> +to allow multicast UDP to listen concurrently across multiple listeners. +The <code>net.ListenMulticastUDP</code> function replaces the old +<code>JoinGroup</code> and <code>LeaveGroup</code> methods. +</p> + +<p> +<em>Updating</em>: +Code that uses the old methods will fail to compile and must be updated by hand. +The semantic change makes it difficult for the fix tool to update automatically. +</p> + +<h3 id="os">The os package</h3> + +<p> +The <code>Time</code> function has been removed; callers should use +the <a href="/pkg/time/#Time"><code>Time</code></a> type from the +<code>time</code> package. +</p> + +<p> +The <code>Exec</code> function has been removed; callers should use +<code>Exec</code> from the <code>syscall</code> package, where available. +</p> + +<p> +The <code>ShellExpand</code> function has been renamed to <a +href="/pkg/os/#ExpandEnv"><code>ExpandEnv</code></a>. +</p> + +<p> +The <a href="/pkg/os/#NewFile"><code>NewFile</code></a> function +now takes a <code>uintptr</code> fd, instead of an <code>int</code>. +The <a href="/pkg/os/#File.Fd"><code>Fd</code></a> method on files now +also returns a <code>uintptr</code>. +</p> + +<p> +There are no longer error constants such as <code>EINVAL</code> +in the <code>os</code> package, since the set of values varied with +the underlying operating system. There are new portable functions like +<a href="/pkg/os/#IsPermission"><code>IsPermission</code></a> +to test common error properties, plus a few new error values +with more Go-like names, such as +<a href="/pkg/os/#ErrPermission"><code>ErrPermission</code></a> +and +<a href="/pkg/os/#ErrNoEnv"><code>ErrNoEnv</code></a>. +</p> + +<p> +The <code>Getenverror</code> function has been removed. To distinguish +between a non-existent environment variable and an empty string, +use <a href="/pkg/os/#Environ"><code>os.Environ</code></a> or +<a href="/pkg/syscall/#Getenv"><code>syscall.Getenv</code></a>. +</p> + + +<p> +The <a href="/pkg/os/#Process.Wait"><code>Process.Wait</code></a> method has +dropped its option argument and the associated constants are gone +from the package. +Also, the function <code>Wait</code> is gone; only the method of +the <code>Process</code> type persists. +</p> + +<p> +The <code>Waitmsg</code> type returned by +<a href="/pkg/os/#Process.Wait"><code>Process.Wait</code></a> +has been replaced with a more portable +<a href="/pkg/os/#ProcessState"><code>ProcessState</code></a> +type with accessor methods to recover information about the +process. +Because of changes to <code>Wait</code>, the <code>ProcessState</code> +value always describes an exited process. +Portability concerns simplified the interface in other ways, but the values returned by the +<a href="/pkg/os/#ProcessState.Sys"><code>ProcessState.Sys</code></a> and +<a href="/pkg/os/#ProcessState.SysUsage"><code>ProcessState.SysUsage</code></a> +methods can be type-asserted to underlying system-specific data structures such as +<a href="/pkg/syscall/#WaitStatus"><code>syscall.WaitStatus</code></a> and +<a href="/pkg/syscall/#Rusage"><code>syscall.Rusage</code></a> on Unix. +</p> + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will drop a zero argument to <code>Process.Wait</code>. +All other changes will be caught by the compiler and must be updated by hand. +</p> + +<h4 id="os_fileinfo">The os.FileInfo type</h4> + +<p> +Go 1 redefines the <a href="/pkg/os/#FileInfo"><code>os.FileInfo</code></a> type, +changing it from a struct to an interface: +</p> + +<pre> + type FileInfo interface { + Name() string // base name of the file + Size() int64 // length in bytes + Mode() FileMode // file mode bits + ModTime() time.Time // modification time + IsDir() bool // abbreviation for Mode().IsDir() + Sys() interface{} // underlying data source (can return nil) + } +</pre> + +<p> +The file mode information has been moved into a subtype called +<a href="/pkg/os/#FileMode"><code>os.FileMode</code></a>, +a simple integer type with <code>IsDir</code>, <code>Perm</code>, and <code>String</code> +methods. +</p> + +<p> +The system-specific details of file modes and properties such as (on Unix) +i-number have been removed from <code>FileInfo</code> altogether. +Instead, each operating system's <code>os</code> package provides an +implementation of the <code>FileInfo</code> interface, which +has a <code>Sys</code> method that returns the +system-specific representation of file metadata. +For instance, to discover the i-number of a file on a Unix system, unpack +the <code>FileInfo</code> like this: +</p> + +<pre> + fi, err := os.Stat("hello.go") + if err != nil { + log.Fatal(err) + } + // Check that it's a Unix file. + unixStat, ok := fi.Sys().(*syscall.Stat_t) + if !ok { + log.Fatal("hello.go: not a Unix file") + } + fmt.Printf("file i-number: %d\n", unixStat.Ino) +</pre> + +<p> +Assuming (which is unwise) that <code>"hello.go"</code> is a Unix file, +the i-number expression could be contracted to +</p> + +<pre> + fi.Sys().(*syscall.Stat_t).Ino +</pre> + +<p> +The vast majority of uses of <code>FileInfo</code> need only the methods +of the standard interface. +</p> + +<p> +The <code>os</code> package no longer contains wrappers for the POSIX errors +such as <code>ENOENT</code>. +For the few programs that need to verify particular error conditions, there are +now the boolean functions +<a href="/pkg/os/#IsExist"><code>IsExist</code></a>, +<a href="/pkg/os/#IsNotExist"><code>IsNotExist</code></a> +and +<a href="/pkg/os/#IsPermission"><code>IsPermission</code></a>. +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/os\.Open/` `/}/`}} +--> f, err := os.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600) + if os.IsExist(err) { + log.Printf("%s already exists", name) + }</pre> + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will update code that uses the old equivalent of the current <code>os.FileInfo</code> +and <code>os.FileMode</code> API. +Code that needs system-specific file details will need to be updated by hand. +Code that uses the old POSIX error values from the <code>os</code> package +will fail to compile and will also need to be updated by hand. +</p> + +<h3 id="os_signal">The os/signal package</h3> + +<p> +The <code>os/signal</code> package in Go 1 replaces the +<code>Incoming</code> function, which returned a channel +that received all incoming signals, +with the selective <code>Notify</code> function, which asks +for delivery of specific signals on an existing channel. +</p> + +<p> +<em>Updating</em>: +Code must be updated by hand. +A literal translation of +</p> +<pre> +c := signal.Incoming() +</pre> +<p> +is +</p> +<pre> +c := make(chan os.Signal) +signal.Notify(c) // ask for all signals +</pre> +<p> +but most code should list the specific signals it wants to handle instead: +</p> +<pre> +c := make(chan os.Signal) +signal.Notify(c, syscall.SIGHUP, syscall.SIGQUIT) +</pre> + +<h3 id="path_filepath">The path/filepath package</h3> + +<p> +In Go 1, the <a href="/pkg/path/filepath/#Walk"><code>Walk</code></a> function of the +<code>path/filepath</code> package +has been changed to take a function value of type +<a href="/pkg/path/filepath/#WalkFunc"><code>WalkFunc</code></a> +instead of a <code>Visitor</code> interface value. +<code>WalkFunc</code> unifies the handling of both files and directories. +</p> + +<pre> + type WalkFunc func(path string, info os.FileInfo, err error) error +</pre> + +<p> +The <code>WalkFunc</code> function will be called even for files or directories that could not be opened; +in such cases the error argument will describe the failure. +If a directory's contents are to be skipped, +the function should return the value <a href="/pkg/path/filepath/#variables"><code>filepath.SkipDir</code></a> +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/STARTWALK/` `/ENDWALK/`}} +--> markFn := func(path string, info os.FileInfo, err error) error { + if path == "pictures" { <span class="comment">// Will skip walking of directory pictures and its contents.</span> + return filepath.SkipDir + } + if err != nil { + return err + } + log.Println(path) + return nil + } + err := filepath.Walk(".", markFn) + if err != nil { + log.Fatal(err) + }</pre> + +<p> +<em>Updating</em>: +The change simplifies most code but has subtle consequences, so affected programs +will need to be updated by hand. +The compiler will catch code using the old interface. +</p> + +<h3 id="regexp">The regexp package</h3> + +<p> +The <a href="/pkg/regexp/"><code>regexp</code></a> package has been rewritten. +It has the same interface but the specification of the regular expressions +it supports has changed from the old "egrep" form to that of +<a href="http://code.google.com/p/re2/">RE2</a>. +</p> + +<p> +<em>Updating</em>: +Code that uses the package should have its regular expressions checked by hand. +</p> + +<h3 id="runtime">The runtime package</h3> + +<p> +In Go 1, much of the API exported by package +<code>runtime</code> has been removed in favor of +functionality provided by other packages. +Code using the <code>runtime.Type</code> interface +or its specific concrete type implementations should +now use package <a href="/pkg/reflect/"><code>reflect</code></a>. +Code using <code>runtime.Semacquire</code> or <code>runtime.Semrelease</code> +should use channels or the abstractions in package <a href="/pkg/sync/"><code>sync</code></a>. +The <code>runtime.Alloc</code>, <code>runtime.Free</code>, +and <code>runtime.Lookup</code> functions, an unsafe API created for +debugging the memory allocator, have no replacement. +</p> + +<p> +Before, <code>runtime.MemStats</code> was a global variable holding +statistics about memory allocation, and calls to <code>runtime.UpdateMemStats</code> +ensured that it was up to date. +In Go 1, <code>runtime.MemStats</code> is a struct type, and code should use +<a href="/pkg/runtime/#ReadMemStats"><code>runtime.ReadMemStats</code></a> +to obtain the current statistics. +</p> + +<p> +The package adds a new function, +<a href="/pkg/runtime/#NumCPU"><code>runtime.NumCPU</code></a>, that returns the number of CPUs available +for parallel execution, as reported by the operating system kernel. +Its value can inform the setting of <code>GOMAXPROCS</code>. +The <code>runtime.Cgocalls</code> and <code>runtime.Goroutines</code> functions +have been renamed to <code>runtime.NumCgoCall</code> and <code>runtime.NumGoroutine</code>. +</p> + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will update code for the function renamings. +Other code will need to be updated by hand. +</p> + +<h3 id="strconv">The strconv package</h3> + +<p> +In Go 1, the +<a href="/pkg/strconv/"><code>strconv</code></a> +package has been significantly reworked to make it more Go-like and less C-like, +although <code>Atoi</code> lives on (it's similar to +<code>int(ParseInt(x, 10, 0))</code>, as does +<code>Itoa(x)</code> (<code>FormatInt(int64(x), 10)</code>). +There are also new variants of some of the functions that append to byte slices rather than +return strings, to allow control over allocation. +</p> + +<p> +This table summarizes the renamings; see the +<a href="/pkg/strconv/">package documentation</a> +for full details. +</p> + +<table class="codetable" frame="border" summary="strconv renames"> +<colgroup align="left" width="50%"></colgroup> +<colgroup align="left" width="50%"></colgroup> +<tr> +<th align="left">Old call</th> +<th align="left">New call</th> +</tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>Atob(x)</td> <td>ParseBool(x)</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>Atof32(x)</td> <td>ParseFloat(x, 32)§</td></tr> +<tr><td>Atof64(x)</td> <td>ParseFloat(x, 64)</td></tr> +<tr><td>AtofN(x, n)</td> <td>ParseFloat(x, n)</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>Atoi(x)</td> <td>Atoi(x)</td></tr> +<tr><td>Atoi(x)</td> <td>ParseInt(x, 10, 0)§</td></tr> +<tr><td>Atoi64(x)</td> <td>ParseInt(x, 10, 64)</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>Atoui(x)</td> <td>ParseUint(x, 10, 0)§</td></tr> +<tr><td>Atoui64(x)</td> <td>ParseUint(x, 10, 64)</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>Btoi64(x, b)</td> <td>ParseInt(x, b, 64)</td></tr> +<tr><td>Btoui64(x, b)</td> <td>ParseUint(x, b, 64)</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>Btoa(x)</td> <td>FormatBool(x)</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>Ftoa32(x, f, p)</td> <td>FormatFloat(float64(x), f, p, 32)</td></tr> +<tr><td>Ftoa64(x, f, p)</td> <td>FormatFloat(x, f, p, 64)</td></tr> +<tr><td>FtoaN(x, f, p, n)</td> <td>FormatFloat(x, f, p, n)</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>Itoa(x)</td> <td>Itoa(x)</td></tr> +<tr><td>Itoa(x)</td> <td>FormatInt(int64(x), 10)</td></tr> +<tr><td>Itoa64(x)</td> <td>FormatInt(x, 10)</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>Itob(x, b)</td> <td>FormatInt(int64(x), b)</td></tr> +<tr><td>Itob64(x, b)</td> <td>FormatInt(x, b)</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>Uitoa(x)</td> <td>FormatUint(uint64(x), 10)</td></tr> +<tr><td>Uitoa64(x)</td> <td>FormatUint(x, 10)</td></tr> +<tr> +<td colspan="2"><hr></td> +</tr> +<tr><td>Uitob(x, b)</td> <td>FormatUint(uint64(x), b)</td></tr> +<tr><td>Uitob64(x, b)</td> <td>FormatUint(x, b)</td></tr> +</table> + +<p> +<em>Updating</em>: +Running <code>go</code> <code>fix</code> will update almost all code affected by the change. +<br> +§ <code>Atoi</code> persists but <code>Atoui</code> and <code>Atof32</code> do not, so +they may require +a cast that must be added by hand; the <code>go</code> <code>fix</code> tool will warn about it. +</p> + + +<h3 id="templates">The template packages</h3> + +<p> +The <code>template</code> and <code>exp/template/html</code> packages have moved to +<a href="/pkg/text/template/"><code>text/template</code></a> and +<a href="/pkg/html/template/"><code>html/template</code></a>. +More significant, the interface to these packages has been simplified. +The template language is the same, but the concept of "template set" is gone +and the functions and methods of the packages have changed accordingly, +often by elimination. +</p> + +<p> +Instead of sets, a <code>Template</code> object +may contain multiple named template definitions, +in effect constructing +name spaces for template invocation. +A template can invoke any other template associated with it, but only those +templates associated with it. +The simplest way to associate templates is to parse them together, something +made easier with the new structure of the packages. +</p> + +<p> +<em>Updating</em>: +The imports will be updated by fix tool. +Single-template uses will be otherwise be largely unaffected. +Code that uses multiple templates in concert will need to be updated by hand. +The <a href="/pkg/text/template/#examples">examples</a> in +the documentation for <code>text/template</code> can provide guidance. +</p> + +<h3 id="testing">The testing package</h3> + +<p> +The testing package has a type, <code>B</code>, passed as an argument to benchmark functions. +In Go 1, <code>B</code> has new methods, analogous to those of <code>T</code>, enabling +logging and failure reporting. +</p> + +<pre><!--{{code "/doc/progs/go1.go" `/func.*Benchmark/` `/^}/`}} +-->func BenchmarkSprintf(b *testing.B) { + <span class="comment">// Verify correctness before running benchmark.</span> + b.StopTimer() + got := fmt.Sprintf("%x", 23) + const expect = "17" + if expect != got { + b.Fatalf("expected %q; got %q", expect, got) + } + b.StartTimer() + for i := 0; i < b.N; i++ { + fmt.Sprintf("%x", 23) + } +}</pre> + +<p> +<em>Updating</em>: +Existing code is unaffected, although benchmarks that use <code>println</code> +or <code>panic</code> should be updated to use the new methods. +</p> + +<h3 id="testing_script">The testing/script package</h3> + +<p> +The testing/script package has been deleted. It was a dreg. +</p> + +<p> +<em>Updating</em>: +No code is likely to be affected. +</p> + +<h3 id="unsafe">The unsafe package</h3> + +<p> +In Go 1, the functions +<code>unsafe.Typeof</code>, <code>unsafe.Reflect</code>, +<code>unsafe.Unreflect</code>, <code>unsafe.New</code>, and +<code>unsafe.NewArray</code> have been removed; +they duplicated safer functionality provided by +package <a href="/pkg/reflect/"><code>reflect</code></a>. +</p> + +<p> +<em>Updating</em>: +Code using these functions must be rewritten to use +package <a href="/pkg/reflect/"><code>reflect</code></a>. +The changes to <a href="http://code.google.com/p/go/source/detail?r=2646dc956207">encoding/gob</a> and the <a href="http://code.google.com/p/goprotobuf/source/detail?r=5340ad310031">protocol buffer library</a> +may be helpful as examples. +</p> + +<h3 id="url">The url package</h3> + +<p> +In Go 1 several fields from the <a href="/pkg/net/url/#URL"><code>url.URL</code></a> type +were removed or replaced. +</p> + +<p> +The <a href="/pkg/net/url/#URL.String"><code>String</code></a> method now +predictably rebuilds an encoded URL string using all of <code>URL</code>'s +fields as necessary. The resulting string will also no longer have +passwords escaped. +</p> + +<p> +The <code>Raw</code> field has been removed. In most cases the <code>String</code> +method may be used in its place. +</p> + +<p> +The old <code>RawUserinfo</code> field is replaced by the <code>User</code> +field, of type <a href="/pkg/net/url/#Userinfo"><code>*net.Userinfo</code></a>. +Values of this type may be created using the new <a href="/pkg/net/url/#User"><code>net.User</code></a> +and <a href="/pkg/net/url/#UserPassword"><code>net.UserPassword</code></a> +functions. The <code>EscapeUserinfo</code> and <code>UnescapeUserinfo</code> +functions are also gone. +</p> + +<p> +The <code>RawAuthority</code> field has been removed. The same information is +available in the <code>Host</code> and <code>User</code> fields. +</p> + +<p> +The <code>RawPath</code> field and the <code>EncodedPath</code> method have +been removed. The path information in rooted URLs (with a slash following the +schema) is now available only in decoded form in the <code>Path</code> field. +Occasionally, the encoded data may be required to obtain information that +was lost in the decoding process. These cases must be handled by accessing +the data the URL was built from. +</p> + +<p> +URLs with non-rooted paths, such as <code>"mailto:dev@golang.org?subject=Hi"</code>, +are also handled differently. The <code>OpaquePath</code> boolean field has been +removed and a new <code>Opaque</code> string field introduced to hold the encoded +path for such URLs. In Go 1, the cited URL parses as: +</p> + +<pre> + URL{ + Scheme: "mailto", + Opaque: "dev@golang.org", + RawQuery: "subject=Hi", + } +</pre> + +<p> +A new <a href="/pkg/net/url/#URL.RequestURI"><code>RequestURI</code></a> method was +added to <code>URL</code>. +</p> + +<p> +The <code>ParseWithReference</code> function has been renamed to <code>ParseWithFragment</code>. +</p> + +<p> +<em>Updating</em>: +Code that uses the old fields will fail to compile and must be updated by hand. +The semantic changes make it difficult for the fix tool to update automatically. +</p> + +<h2 id="cmd_go">The go command</h2> + +<p> +Go 1 introduces the <a href="/cmd/go/">go command</a>, a tool for fetching, +building, and installing Go packages and commands. The <code>go</code> command +does away with makefiles, instead using Go source code to find dependencies and +determine build conditions. Most existing Go programs will no longer require +makefiles to be built. +</p> + +<p> +See <a href="/doc/code.html">How to Write Go Code</a> for a primer on the +<code>go</code> command and the <a href="/cmd/go/">go command documentation</a> +for the full details. +</p> + +<p> +<em>Updating</em>: +Projects that depend on the Go project's old makefile-based build +infrastructure (<code>Make.pkg</code>, <code>Make.cmd</code>, and so on) should +switch to using the <code>go</code> command for building Go code and, if +necessary, rewrite their makefiles to perform any auxiliary build tasks. +</p> + +<h2 id="cmd_cgo">The cgo command</h2> + +<p> +In Go 1, the <a href="/cmd/cgo">cgo command</a> +uses a different <code>_cgo_export.h</code> +file, which is generated for packages containing <code>//export</code> lines. +The <code>_cgo_export.h</code> file now begins with the C preamble comment, +so that exported function definitions can use types defined there. +This has the effect of compiling the preamble multiple times, so a +package using <code>//export</code> must not put function definitions +or variable initializations in the C preamble. +</p> + +<h2 id="releases">Packaged releases</h2> + +<p> +One of the most significant changes associated with Go 1 is the availability +of prepackaged, downloadable distributions. +They are available for many combinations of architecture and operating system +(including Windows) and the list will grow. +Installation details are described on the +<a href="/doc/install">Getting Started</a> page, while +the distributions themselves are listed on the +<a href="http://code.google.com/p/go/downloads/list">downloads page</a>. + + +</div> + +<div id="footer"> +Build version go1.0.1.<br> +Except as <a href="http://code.google.com/policies.html#restrictions">noted</a>, +the content of this page is licensed under the +Creative Commons Attribution 3.0 License, +and code is licensed under a <a href="/LICENSE">BSD license</a>.<br> +<a href="/doc/tos.html">Terms of Service</a> | +<a href="http://www.google.com/intl/en/privacy/privacy-policy.html">Privacy Policy</a> +</div> + +<script type="text/javascript"> +(function() { + var ga = document.createElement("script"); ga.type = "text/javascript"; ga.async = true; + ga.src = ("https:" == document.location.protocol ? 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