interrupt: fix send on closed

If we get a signal while shutting down, we could end up sending on a closed
channel.

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

cmd/ipfs/util/signal.go

@@ -15,38 +15,43 @@ import (
 // IntrHandler helps set up an interrupt handler that can
 // be cleanly shut down through the io.Closer interface.
 type IntrHandler struct {
-	sig chan os.Signal
-	wg  sync.WaitGroup
+	closing chan struct{}
+	wg      sync.WaitGroup
 }
 
 func NewIntrHandler() *IntrHandler {
-	ih := &IntrHandler{}
-	ih.sig = make(chan os.Signal, 1)
-	return ih
+	return &IntrHandler{closing: make(chan struct{})}
 }
 
 func (ih *IntrHandler) Close() error {
-	close(ih.sig)
+	close(ih.closing)
 	ih.wg.Wait()
 	return nil
 }
 
 // Handle starts handling the given signals, and will call the handler
-// callback function each time a signal is catched. The function is passed
+// callback function each time a signal is caught. The function is passed
 // the number of times the handler has been triggered in total, as
 // well as the handler itself, so that the handling logic can use the
 // handler's wait group to ensure clean shutdown when Close() is called.
 func (ih *IntrHandler) Handle(handler func(count int, ih *IntrHandler), sigs ...os.Signal) {
-	signal.Notify(ih.sig, sigs...)
+	notify := make(chan os.Signal, 1)
+	signal.Notify(notify, sigs...)
 	ih.wg.Add(1)
 	go func() {
 		defer ih.wg.Done()
+		defer signal.Stop(notify)
+
 		count := 0
-		for range ih.sig {
-			count++
-			handler(count, ih)
+		for {
+			select {
+			case <-ih.closing:
+				return
+			case <-notify:
+				count++
+				handler(count, ih)
+			}
 		}
-		signal.Stop(ih.sig)
 	}()
 }