Using Bluebird's Promise.Coroutine to write asynchronous code "synchronously" in Node 7.4.0 and Express 4

main.js

'use strict'
const express = require('express');
const app = express();
const Promise = require('bluebird');
const {coroutine: co} = require('bluebird'); //Alias coroutine
app.listen(3000, function () {
  console.log('Example app listening on port 3000!')
})

app.get('/', (req, res)=>{
	console.log('hit')
	//Create the self invoking function
	co(function* () {
		try {
			let _first = yield first();
			let _second = yield second();
			let _final = yield putittogether(_first, _second);
			//Respond
			res.json(_final);
		} catch(e) {
			//If there was a rejection we will catch it here. 
			res.json(e);
		}
	})();
})


function first() {
	return new Promise((resolve, reject)=>{
		setTimeout(()=>{
			resolve(1);
		}, 2000)
	})
}

function second() {
	return new Promise((resolve, reject)=>{
		setTimeout(()=>{
			resolve(2);
		}, 1)
	})
}

function putittogether(first, second) {
	return new Promise((resolve, reject)=>{
		resolve(first + second);
	})
}