nit: use if-let

src/bin/mgen-server.rs

@@ -259,10 +259,10 @@ async fn send_messages<T: Send + Sync + tokio::io::AsyncWrite>(
     let (mut current_socket, mut current_watch) = socket_updater.recv().await;
     let mut message_cache = None;
     loop {
-        let message = if message_cache.is_none() {
-            msg_rcv.recv().await.expect("message channel closed")
+        let message = if let Some(message) = message_cache {
+            message
         } else {
-            message_cache.unwrap()
+            msg_rcv.recv().await.expect("message channel closed")
         };
         if message.write_all_to(&mut current_socket).await.is_err()
             || current_socket.flush().await.is_err()