using mongoose 4.11.0

User.js

const mongoose = require('mongoose')
mongoose.Promise = require('bluebird')  // optional, use this to get rid of 
                                        // the mpromise DeprecationWarning
const conn = mongoose.createConnection('mongodb://localhost/testDB')
const Schema = mongoose.Schema

const UserSchema = new Schema({
	username: String,
	email: String
})

const User = conn.model('User', UserSchema)
module.exports = User