Avoid printing a signal error when closing a connection

djs55 · djs55 · commit 18466a2b7650 · 2021-05-24T19:37:58.000+01:00
Previously I would see:
```
dave@m1 cli % ./build/docker run -it --init ubuntu
root@7f9fc6aee300:/# exit
Unsupported signal: &lt;nil&gt;. Discarding.
```

Signed-off-by: David Scott &lt;dave@recoil.org&gt;
diff --git a/cli/command/container/signals.go b/cli/command/container/signals.go
@@ -16,13 +16,19 @@ import (
 // The channel you pass in must already be setup to receive any signals you want to forward.
 func ForwardAllSignals(ctx context.Context, cli command.Cli, cid string, sigc <-chan os.Signal) {
 	var s os.Signal
+	var ok bool
 	for {
 		select {
-		case s = <-sigc:
+		case s, ok = <-sigc:
 		case <-ctx.Done():
 			return
 		}
 
+		if !ok {
+			// channel closed: session is over
+			return
+		}
+
 		if s == signal.SIGCHLD || s == signal.SIGPIPE {
 			continue
 		}
