[koa] mount exported router

index.js

(function() {
  'use strict';
  /* jshint esnext:true */

  var koa = require('koa');
  var app = koa();

  var PORT = process.env.PORT || 3333;

  var router = require('./router');

  app.use(router.routes());

  app.listen(PORT);

}());

router.js

(function() {
  'use strict';
  /* jshint esnext:true */

  var Router = require('koa-router');
  module.exports = exports = new Router()
    .get('/a', routeA)
    .get('/b', routeB);

  function* routeA(next) {
    this.status = 202;
    this.body = {
      message: 'accepted'
    };

    yield (next);
  }

  function* routeB(next) {
    this.status = 410;
    this.body = {
      message: 'gone'
    };

    yield (next);
  }

}());