写入 websocket 流

Question

tungstenite 我正在使用此示例连接到 websocket 服务器并从那里使用write.send

let connect_addr = env::args()
    .nth(1)
    .unwrap_or_else(|| panic!("this program requires at least one argument"));

let url = url::Url::parse(&connect_addr).unwrap();

let (stdin_tx, stdin_rx) = futures_channel::mpsc::unbounded();
tokio::spawn(read_stdin(stdin_tx));

let (ws_stream, _) = connect_async(url).await.expect("Failed to connect");
println!("WebSocket handshake has been successfully completed");

let (write, read) = ws_stream.split();

## THIS DOESNT WORK ###
write.send(Message::Text(format!("{}", "HELLO!")))
            .await
            .expect("Failed to send message");

我无法让写入工作。我得到：

error[E0599]: no method named `send` found for struct `futures_util::stream::stream::split::SplitSink<tokio_tungstenite::WebSocketStream<tokio_tungstenite::stream::Stream<tokio::net::tcp::stream::TcpStream, tokio_native_tls::TlsStream<tokio::net::tcp::stream::TcpStream>>>, tungstenite::protocol::message::Message>` in the current scope
   --> src/main.rs:28:15
    |
28  |         write.send(Message::Text(format!("{}", 8)))
    |               ^^^^ method not found in `futures_util::stream::stream::split::SplitSink<tokio_tungstenite::WebSocketStream<tokio_tungstenite::stream::Stream<tokio::net::tcp::stream::TcpStream, tokio_native_tls::TlsStream<tokio::net::tcp::stream::TcpStream>>>, tungstenite::protocol::message::Message>`
    |
   ::: ../futures-util-0.3.5/src/sink/mod.rs:207:8
    |
207 |     fn send(&mut self, item: Item) -> Send<'_, Self, Item>
    |        ----
    |        |
    |        the method is available for `std::boxed::Box<futures_util::stream::stream::split::SplitSink<tokio_tungstenite::WebSocketStream<tokio_tungstenite::stream::Stream<tokio::net::tcp::stream::TcpStream, tokio_native_tls::TlsStream<tokio::net::tcp::stream::TcpStream>>>, tungstenite::protocol::message::Message>>` here
    |        the method is available for `std::sync::Arc<futures_util::stream::stream::split::SplitSink<tokio_tungstenite::WebSocketStream<tokio_tungstenite::stream::Stream<tokio::net::tcp::stream::TcpStream, tokio_native_tls::TlsStream<tokio::net::tcp::stream::TcpStream>>>, tungstenite::protocol::message::Message>>` here
    |        the method is available for `std::rc::Rc<futures_util::stream::stream::split::SplitSink<tokio_tungstenite::WebSocketStream<tokio_tungstenite::stream::Stream<tokio::net::tcp::stream::TcpStream, tokio_native_tls::TlsStream<tokio::net::tcp::stream::TcpStream>>>, tungstenite::protocol::message::Message>>` here