Add SIGHUP support

Fixes adnanh#352

docs/Webhook-Parameters.md

@@ -44,7 +44,9 @@ Usage of webhook:
 Use any of the above specified flags to override their default behavior.
 
 # Live reloading hooks
-If you are running an OS that supports USR1 signal, you can use it to trigger hooks reload from hooks file, without restarting the webhook instance.
+If you are running an OS that supports the HUP or USR1 signal, you can use it to trigger hooks reload from hooks file, without restarting the webhook instance.
 ```bash
 kill -USR1 webhookpid
+
+kill -HUP webhookpid
 ```

signals.go

@@ -14,6 +14,7 @@ func setupSignals() {
 
 	signals = make(chan os.Signal, 1)
 	signal.Notify(signals, syscall.SIGUSR1)
+	signal.Notify(signals, syscall.SIGHUP)
 
 	go watchForSignals()
 }
@@ -23,11 +24,16 @@ func watchForSignals() {
 
 	for {
 		sig := <-signals
-		if sig == syscall.SIGUSR1 {
+		switch sig {
+		case syscall.SIGUSR1:
 			log.Println("caught USR1 signal")
 
 			reloadAllHooks()
-		} else {
+		case syscall.SIGHUP:
+			log.Println("caught HUP signal")
+
+			reloadAllHooks()
+		default:
 			log.Printf("caught unhandled signal %+v\n", sig)
 		}
 	}