Please answer these questions before submitting your issue. Thanks!

1. What version of Go are you using (go version)?
   go version go1.6 darwin/amd64
2. What operating system and processor architecture are you using (go env)?
   GOARCH="amd64"
   GOBIN=""
   GOEXE=""
   GOHOSTARCH="amd64"
   GOHOSTOS="darwin"
   GOOS="darwin"
   GOPATH="/Users/ryangao/go"
   GORACE=""
   GOROOT="/Users/ryangao/homebrew/Cellar/go/1.6/libexec"
   GOTOOLDIR="/Users/ryangao/homebrew/Cellar/go/1.6/libexec/pkg/tool/darwin_amd64"
   GO15VENDOREXPERIMENT="1"
   CC="clang"
   GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fno-common"
   CXX="clang++"
   CGO_ENABLED="1"
3. What did you do?
   Run "go vet" on code from https://play.golang.org/p/mUiuNfZDHT
4. What did you expect to see?
   Expect "go vet" warns about error mentioned in
   https://golang.org/doc/faq#closures_and_goroutines
5. What did you see instead?
   No warning issued.