code review 6903061: cmd/go: handle os signals

src/cmd/go/signal.go

+// 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 main
+
+import (
+        "os"
+        "os/signal"
+        "sync"
+)
+
+// interrupted is closed, if go process is interrupted.
+var interrupted = make(chan struct{})
+
+func closeInterrupted() {
+        close(interrupted)
+}
+
+var onceCloseInterrupted sync.Once
+
+// processSignals setups signal handler.
+func processSignals() {
+        sig := make(chan os.Signal)
+        signal.Notify(sig, signalsToIgnore...)
+        go func() {
+                for _ = range sig {
+                        onceCloseInterrupted.Do(closeInterrupted)

[dave_cheney.net, 2012/12/14 00:16:45]

I'm sorry to harp on this. I don't think the sync.Once handler is adding
anything that 

go func() {
   <- sig
   close(closeInterrupted)
}()

wouldn't do

+                        return
+                }
+        }()
+}
+
+var onceProcessSignals sync.Once
+
+// startSigHandlers start signal handlers.
+func startSigHandlers() {
+        onceProcessSignals.Do(processSignals)
+}