You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: main.rs
    path of file: ./repos/roa/integration/websocket-example/src
    
    the code of the file until where you have to start completion: use std::borrow::Cow;
use std::error::Error as StdError;
use std::sync::Arc;

use futures::stream::{SplitSink, SplitStream};
use futures::{SinkExt, StreamExt};
use http::Method;
use roa::logger::logger;
use roa::preload::*;
use roa::router::{allow, RouteTable, Router, RouterError};
use roa::websocket::tungstenite::protocol::frame::coding::CloseCode;
use roa::websocket::tungstenite::protocol::frame::CloseFrame;
use roa::websocket::tungstenite::Error as WsError;
use roa::websocket::{Message, SocketStream, Websocket};
use roa::{App, Context};
use slab::Slab;
use tokio::sync::{Mutex, RwLock};
use tracing::{debug, error, info, warn};
use tracing_subscriber::EnvFilter;

type S
    
    async fn echo() -> Result<(), Box<dyn StdError>> {
        let channel = SyncChannel::new();
        let app = App::state(channel.clone()).end(route("/")?);
        let (addr, server) = app.run()?;
        tokio::task::spawn(server);
        let (ws_stream, _) = connect_async(format!("ws://{}/chat", addr)).await?;
        let (mut sender, mut recv) = ws_stream.split();
        tokio::time::sleep(Duration::from_secs(1)).await;
        assert_eq!(1, channel.0.read().await.len());

        // ping
        sender
            .send(Message::Ping(b"Hello, World!".to_vec()))
            .await?;
        let msg = recv.next().await.unwrap()?;
        assert!(msg.is_pong());
        assert_eq!(b"Hello, World!".as_ref(), msg.into_data().as_slice());

        // close
        sender.send(Message::Close(None)).await?;
        tokio::time::sleep(Duration::from_secs(1)).await;
        assert_eq!(0, channel.0.read().await.len());
        Ok(())
    }