index.js

//import koa
 var Koa = require('koa');

//import all the routes
 var special = require('./routes/welcome');
 var admin = require('./routes/admin');
 var articles = require('./routes/articles.js');

 //create a koa instance and store it in app variable
var app = new Koa();

 ////apply the routes as a middleware
 app.use(special.routes());
 app.use(articles.routes());

 //if there is no environment variable set for port number
 //use a default value of 3000
 var port = process.env.PORT || 3000;

//run the werver on port 3000
 app.listen(port);