can't create a websocket sever correctly by express-ws middleware
<p>I'm writing a websocket server using node.js and express, and I use the express-ws middleware to help me. But the client can't connect the server.Below is my code.</p>

<p>app.js:</p>

<pre><code>var app = express();
var expressWs = require("express-ws")(app);
...
var webso = require("./routes/ws");
app.use("/chat",webso);
</code></pre>

<p>routes/ws.js:</p>

<pre><code>var express = require('express');
var router = express.Router();

router.ws("/",function(ws,req){
  console.log("socket from client")
  ws.on('message',function(msg){
    ws.send('back from node');
  })
});
module.exports=router;
</code></pre>

<p>the client:</p>

<pre><code>wx.connectSocket({
        url:"ws://localhost:3000/chat",
        success(){
            console.log("success")
        },
        fail(){
            console.log("err")
        },
        complete(){
            console.log("done");
        }
    });
</code></pre>

<p>the client can't connect the websocket server:</p>

<pre><code>asdebug.js:1 WebSocket connection to 'ws://localhost:3000/chat' failed: Connection closed before receiving a handshake response
</code></pre>

<p>I think something wrong I has made at the express server.I need your help.</p>