Handle missed subcommand

src/main.rs

@@ -77,7 +77,11 @@ fn parse_args() -> Command {
                 .help("The multiaddr of the remote peer"),
         );
 
-    app = app.subcommand(serve).subcommand(create_tunnel_server);
+    app = app
+        .arg_required_else_help(true)
+        .subcommand(serve)
+        .subcommand(create_tunnel_server);
+
     app
 }
 
@@ -176,13 +180,15 @@ async fn main() {
         .with_env_filter(tracing_subscriber::EnvFilter::from_default_env())
         .try_init();
 
-    let args = parse_args().get_matches();
-
-    if let Some(args) = args.subcommand_matches("serve") {
-        serve(args).await;
-    }
+    let cmd = parse_args();
 
-    if let Some(args) = args.subcommand_matches("create_tunnel_server") {
-        create_tunnel_server(args).await;
+    match cmd.get_matches().subcommand() {
+        Some(("serve", args)) => {
+            serve(args).await;
+        }
+        Some(("create_tunnel_server", args)) => {
+            create_tunnel_server(args).await;
+        }
+        _ => unreachable!(),
     }
 }