next() call in express-ws module in nodejs

I came across a sample code for my webserver using express-ws for reliable Websocket connection between my server and client browser. The code will start listening in port 3000 for websocket connection.

var express = require('express');

var app = express();

var expressWs = require('express-ws')(app);



app.use(function (req, res, next) {

    console.log('middleware');

    req.testing = 'testing';

    return next();

});



app.get('/', function(req, res, next){

  console.log('get route', req.testing);

  res.end();

});



app.ws('/', function(ws, req) {

  ws.on('message', function(msg) {

    console.log(msg);

  });

  console.log('socket', req.testing);

});



server.listen(3000);