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// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package sync_test
import (
"fmt"
"net/http"
"sync"
)
// This example fetches several URLs concurrently,
// using a WaitGroup to block until all the fetches are complete.
func ExampleWaitGroup() {
var wg sync.WaitGroup
var urls = []string{
"http://www.golang.org/",
"http://www.google.com/",
"http://www.somestupidname.com/",
}
for _, url := range urls {
// Increment the WaitGroup counter.
wg.Add(1)
// Launch a goroutine to fetch the URL.
go func(url string) {
// Decrement the counter when the goroutine completes.
defer wg.Done()
// Fetch the URL.
http.Get(url)
}(url)
}
// Wait for all HTTP fetches to complete.
wg.Wait()
}
func ExampleOnce() {
var once sync.Once
onceBody := func() {
fmt.Println("Only once")
}
done := make(chan bool)
for i := 0; i < 10; i++ {
go func() {
once.Do(onceBody)
done <- true
}()
}
for i := 0; i < 10; i++ {
<-done
}
// Output:
// Only once
}
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