[2306] Error when using process.env.baseURL

I'm using async/await with asnycData, when I do this, it works fine:

async asyncData({env}) {
    let data = await axios.get('http://localhost:3000/api/')
    return {products: data}
}

However, when I use process.env.baseURL instead of http://localhost:3000, it throws an error:

async asyncData({env}) {
    let data = await axios.get(process.env.baseURL + '/api/')
    return {products: data}
}

Error:

connect ECONNREFUSED 127.0.0.1:80

util.js:1031:13     Object._errnoException
Missing stack frames

util.js:1052:20     _exceptionWithHostPort
Missing stack frames

net.js:1195:14     TCPConnectWrap.afterConnect [as oncomplete]
Missing stack frames

I have my baseURL set in my nuxt config like this:

env: {
    baseUrl: process.env.BASE_URL || 'http://localhost:3000'
}

I am using a custom server for my API endpoints like this:

const { Nuxt, Builder } = require('nuxt')

const app        = require('express')()
const bodyParser = require('body-parser')
const mongoose   = require('mongoose')

const host = process.env.HOST || '127.0.0.1'
const port = process.env.PORT || 3000

// DATABASE
// ==============================================

mongoose.connect('MONGO DB DETAILS')
mongoose.Promise = Promise

// CONFIG
// ==============================================

app.use(bodyParser.json())

// MODELS
// ==============================================
const Product = require('./source/models/product');

// ROUTES
// ==============================================

app.get('/api', async(req, res) => {
   try {
      const products = await Products.find();
      return res.json(products);
    }
    catch (error) {
      console.log(error)
    }
}
// START
// ==============================================

const config = require('../nuxt.config.js')
const nuxt   = new Nuxt(config)

if(!(process.env.NODE_ENV === 'production')) {
  const builder = new Builder(nuxt)
  builder.build()
}

app.use(nuxt.render)
app.listen(port, host)

I'm using the latest 1.0.0-rc11 version with node 9.2.0.

Thanks. Anthony