【Rust】websocketのreceive

echoサーバにリクエストを送り、このレスポンスが、”foo”なので、received_msgがfooだと思っていたが、

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut ws = WebSocket::connect("wss://echo.websocket.org/").await?;
    ws.send_text("foo".to_string()).await?;
    ws.receive().await?;
    if let Frame::Text { payload: received_msg, .. } =  ws.receive().await? {
        println!("{}", received_msg);
    }
    ws.close(None).await?;
    Ok(())
}  

Finished `dev` profile [unoptimized + debuginfo] target(s) in 1.60s
Running `target/debug/app`
foo

以下のように書くと、”Request served by *****”がレスポンスで帰ってくる。websocketのreceiveは以下のように書くのが正解

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut ws = WebSocket::connect("wss://echo.websocket.org/").await?;
    ws.send_text("foo".to_string()).await?;
    if let Frame::Text { payload: received_msg, .. } =  ws.receive().await? {
        println!("{}", received_msg);
    }
    ws.close(None).await?;
    Ok(())
}   

Finished `dev` profile [unoptimized + debuginfo] target(s) in 2.07s
Running `target/debug/app`
Request served by 7811941c69e658