implement graceful shutdown to webhook mode

ensures all pending tasks are finished before quit.

cmd/listen.go

@@ -70,7 +70,7 @@ is up to you, eg. Nginx, Apache, or even a simple Go server.
 			GitPass: token,
 		}
 
-		s, err := lib.UseWebhook(bind, cfg)
+		s, r, err := lib.UseWebhook(bind, cfg)
 		if err != nil {
 			fmt.Println("cannot create server: ", err)
 			return
@@ -85,7 +85,11 @@ is up to you, eg. Nginx, Apache, or even a simple Go server.
 		defer stop()
 
 		fmt.Println("starting server")
-		httptask.Server(s, task.Timeout(10*time.Second)).Run(ctx)
+		task.Wait(
+			httptask.Server(s, task.Timeout(10*time.Second)),
+			r.Run,
+		).Run(ctx)
+
 	},
 }