Make chat-client reads cancellation safe (#713)

* Make chat-client reads cancellation safe

* Update chat-app references

src/exercises/concurrency/chat-app.md

@@ -29,7 +29,7 @@ API.
   Websocket Stream.
 - [SinkExt::send()][4] implemented by `WebsocketStream`: for asynchronously
   sending messages on a Websocket Stream.
-- [BufReader::read_line()][5]: for asynchronously reading user messages
+- [Lines::next_line()][5]: for asynchronously reading user messages
   from the standard input.
 - [Sender::subscribe()][6]: for subscribing to a broadcast channel.
 
@@ -104,6 +104,6 @@ $ cargo run --bin client
 [2]: https://docs.rs/tokio-websockets/0.3.2/tokio_websockets/
 [3]: https://docs.rs/tokio-websockets/0.3.2/tokio_websockets/proto/struct.WebsocketStream.html#method.next
 [4]: https://docs.rs/futures-util/0.3.28/futures_util/sink/trait.SinkExt.html#method.send
-[5]: https://docs.rs/tokio/latest/tokio/io/trait.AsyncBufReadExt.html#method.read_line
+[5]: https://docs.rs/tokio/latest/tokio/io/struct.Lines.html#method.next_line
 [6]: https://docs.rs/tokio/latest/tokio/sync/broadcast/struct.Sender.html#method.subscribe
 [7]: https://doc.rust-lang.org/cargo/reference/cargo-targets.html#binaries

src/exercises/concurrency/chat-async/src/bin/client.rs

@@ -25,12 +25,11 @@ async fn main() -> Result<(), tokio_websockets::Error> {
         .await?;
 
     let stdin = tokio::io::stdin();
-    let mut stdin = BufReader::new(stdin);
+    let mut stdin = BufReader::new(stdin).lines();
 
     // ANCHOR_END: setup
     // Continuous loop for concurrently sending and receiving messages.
     loop {
-        let mut line = String::new();
         tokio::select! {
             incoming = ws_stream.next() => {
                 match incoming {
@@ -39,10 +38,10 @@ async fn main() -> Result<(), tokio_websockets::Error> {
                     None => return Ok(()),
                 }
             }
-            res = stdin.read_line(&mut line) => {
+            res = stdin.next_line() => {
                 match res {
-                    Ok(0) => return Ok(()),
-                    Ok(_) => ws_stream.send(Message::text(line.trim_end().to_string())).await?,
+                    Ok(None) => return Ok(()),
+                    Ok(Some(line)) => ws_stream.send(Message::text(line.to_string())).await?,
                     Err(err) => return Err(err.into()),
                 }
             }