Nodejs第二课

"dependencies": {
  "express": "^4.13.1",
  "utility": "^1.4.0"
}

//引入依赖
var express = require('express');
var utility = require('utility');
//建立实例
var app = express();
app.get('/', function(req, res){
    //取值
    var q = req.query.q;
    //使用utility模块计算md5
    var md5Value = utility.md5(q);
    res.send(md5Value);
});
app.listen(3000, function(req, res){
    console.log('app is running at port 3000');
});

TypeError: Not a string or buffer
   at TypeError (native)
   at Hash.update (crypto.js:119:16)
   at Object.hash (/Users/admin/Desktop/lesson2/node_modules/utility/lib/crypto.js:31:7)
   at Object.md5 (/Users/admin/Desktop/lesson2/node_modules/utility/lib/crypto.js:44:18)
   at /Users/admin/Desktop/lesson2/app.js:9:25
   at Layer.handle [as handle_request] (/Users/admin/Desktop/lesson2/node_modules/express/lib/router/layer.js:95:5)
   at next (/Users/admin/Desktop/lesson2/node_modules/express/lib/router/route.js:131:13)
   at Route.dispatch (/Users/admin/Desktop/lesson2/node_modules/express/lib/router/route.js:112:3)
   at Layer.handle [as handle_request] (/Users/admin/Desktop/lesson2/node_modules/express/lib/router/layer.js:95:5)
   at /Users/admin/Desktop/lesson2/node_modules/express/lib/router/index.js:277:22

var md5Value = utility.md5(q);
        res.send(md5Value);