multi: wrap logger to request shutdown from signal on critical error

This commit adds a shutdown logger which will send a request for
shutdown on critical errors. It uses the signal package to request safe
shutdown of the daemon. Since we init our logs in config validation,
we add a started channel to the signal package to prevent the case where
we have a critical log after the ShutdownLogger has started but before
the daemon has started listening for intercepts. In this case, we just
ignore the shutdown request.

cmd/lncli/cmd_open_channel.go

@@ -414,7 +414,10 @@ func openChannelPsbt(ctx *cli.Context, client lnrpc.LightningClient,
 	if err != nil {
 		return fmt.Errorf("opening stream to server failed: %v", err)
 	}
-	signal.Intercept()
+
+	if err := signal.Intercept(); err != nil {
+		return err
+	}
 
 	// We also need to spawn a goroutine that reads from the server. This
 	// will copy the messages to the channel as long as they come in or add

cmd/lnd/main.go

@@ -19,7 +19,10 @@ func main() {
 	}
 
 	// Hook interceptor for os signals.
-	signal.Intercept()
+	if err := signal.Intercept(); err != nil {
+		_, _ = fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
 
 	// Call the "real" main in a nested manner so the defers will properly
 	// be executed in the case of a graceful shutdown.