Unable to find module 'server', custom added express server

I've added an expressJS app inside my ember app so I can provide a backend API for my ember app.

My process:

npm install express --save

I created a folder called "server" in the route of my ember application and inside that a file called "server.js".

Yesterday I had it working fine, I already had my ember app running via ember s and tested out the express app using nodemon server/server.js and checking the endpoints I created with Postman.

However this morning when I've tried to run ember s I'm given the following error:

C:\Sandbox\tsodash>ember s
version: 2.3.0-beta.2
Cannot find module 'C:\Sandbox\tsodash\server'
Error: Cannot find module 'C:\Sandbox\tsodash\server'
    at Function.Module._resolveFilename (module.js:339:15)
    at Function.Module._load (module.js:290:25)
    at Module.require (module.js:367:17)
    at require (internal/module.js:16:19)
    at Project.require (C:\Sandbox\tsodash\node_modules\ember-cli\lib\models\project.js:281:12)
    at Class.module.exports.Task.extend.processAppMiddlewares (C:\Sandbox\tsodash\node_modules\ember-cli\lib\tasks\server\express-server.js:115:33)
    at Class.<anonymous> (C:\Sandbox\tsodash\node_modules\ember-cli\lib\tasks\server\express-server.js:220:21)
    at lib$rsvp$$internal$$tryCatch (C:\Sandbox\tsodash\node_modules\ember-cli\node_modules\rsvp\dist\rsvp.js:1036:16)
    at lib$rsvp$$internal$$invokeCallback (C:\Sandbox\tsodash\node_modules\ember-cli\node_modules\rsvp\dist\rsvp.js:1048:17)
    at C:\Sandbox\tsodash\node_modules\ember-cli\node_modules\rsvp\dist\rsvp.js:331:11

Naturally I assumed I just needed to use modules.exports = function(){ //..expressjs code}

Full Code

var express = require('express');
var app = express();
var bodyParser = require('body-parser');
var request = require('request');
var btoa = require('btoa');
var config = require('./config');
var _ = require('lodash');


module.exports = function(){

  var endPoints = config.endPoints;
  app.use(bodyParser.urlencoded({
    extended: true
  }));
  app.use(bodyParser.json());

  var port = process.env.PORT || 4200;

  var router = express.Router();

  // middleware to use for all requests
  router.use(function (req, res, next) {
    // do logging
    console.log('Something is happening.');
    next(); // make sure we go to the next routes and don't stop here
  });


  router.get('/', function (req, res) {
    res.json({
      message: 'TSO Git Dash'
    });
  });

  //  ..      
  app.use('/api', router);

  app.listen(port);
  console.log('Magic happens on port: ' + port);
}

Still no avail.

Folder structure:

Any ideas? I'm assuming it's something simple that I've missed. But I'm stumped.