Remove signal handling channels correctly

The "break" here only break out from the inner select statement.
The for loop is keep running and signal.Stop() won't be called.

Seems that is the cause of #198.

Signed-off-by: Kazuyoshi Kato <[email protected]>

Author: kzys

machine.go

@@ -948,13 +948,16 @@ func (m *Machine) setupSignals() {
 	signal.Notify(sigchan, signals...)
 
 	go func() {
+	ForLoop:
 		for {
 			select {
 			case sig := <-sigchan:
-				m.logger.Printf("Caught signal %s", sig)
+				m.logger.Debugf("Caught signal %s", sig)
+				// Some signals kill the process, some of them are not.
 				m.cmd.Process.Signal(sig)
 			case <-m.exitCh:
-				break
+				// And if a signal kills the process, we can stop this for loop and remove sigchan.
+				break ForLoop
 			}
 		}