Make gofmt check fail if there are any matching files

gofmt doesn't return an exit code 1 if there are matching files:
https://github.com/golang/go/issues/24230

To fix this, use the same trick we use in Workhorse to parse output.
Also add a `make fmt` step to format all the code properly.

1 files changed, 4 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 88daed3..632c324 100644
--- a/Makefile
+++ b/Makefile
@@ -13,7 +13,10 @@ validate: verify test
 verify: verify_golang
 
 verify_golang:
-	gofmt -s -l $(GO_SOURCES)
+	gofmt -s -l $(GO_SOURCES) | awk '{ print } END { if (NR > 0) { print "Please run make fmt"; exit 1 } }'
+
+fmt:
+	gofmt -w -s $(GO_SOURCES)
 
 test: test_ruby test_golang