Express.io express.Router() is returning undefined

Question

I am in the process of switching from express to express.io for my web app, but when I run the app it throws an error, seems to have something to do with express.io's express.Route() returning undefined, is there a way I can fix this?

/home/zunon/Development/Projects/xKout/router.js:35
router.get('/randomcard', function(req, res) {
      ^

TypeError: Cannot read property 'get' of undefined
    at Object.<anonymous> (/home/zunon/Development/Projects/xKout/router.js:35:7)
    at Module._compile (module.js:413:34)
    at Object.Module._extensions..js (module.js:422:10)
    at Module.load (module.js:357:32)
    at Function.Module._load (module.js:314:12)
    at Module.require (module.js:367:17)
    at require (internal/module.js:16:19)
    at Object.<anonymous> (/home/zunon/Development/Projects/xKout/xkout.js:6:10)
    at Module._compile (module.js:413:34)
    at Object.Module._extensions..js (module.js:422:10)

Here is my main xkout.coffee file which is compiled into xkout.js

express = require 'express.io'
router = require './router'
app = express()
app.http().io()

app.set 'view engine', 'jade'
app.set 'views', './views'

app.use '/', router
app.use '/public', express.static './public'

app.listen 3000, () ->
    console.log 'Listening on 3000'
    return

And here's my router.coffee which is my routing middleware

express = require 'express.io'
router = express.Router()

createCardName = ->
    position = Math.floor Math.random() * cards.length
    cards.splice position, 1

resetCards = ->
    for i in [1..13] by 1
        cards[i - 1] = "club#{i}"
        cards[i + 12] = "dmnd#{i}"
        cards[i + 25] = "hart#{i}"
        cards[i + 38] = "spad#{i}"
        if i < 3
            cards[i + 51] = "joke#{i}"

cards = []

resetCards()

router.get '/randomcard', (req, res) ->
        cardNames = {}
        for i in [1..6] by 1
            cardNames[i] = []
            for j in [1..9] by 1
                cardNames[i][j] = createCardName()
        console.log cardNames
        resetCards()
        res.render 'randomcard', {cardNames}
        return

module.exports = router

I have found that other people have asked this question before and got no answer: https://stackoverflow.com/questions/31222845/how-to-use-express-router-with-express-io