server.js

const express = require('express')
const next = require('next')
const config = require('./next.config.js')

const dev = process.env.NODE_ENV !== 'production'
const app = next({ dev })
const handle = app.getRequestHandler()

const prefix = config.assetPrefix

app.prepare()
.then(() => {
  const server = express()
  const router = express.Router()

  // use next routes
  server.use(`${prefix}`, router)
  server.use(`${prefix}/static`, express.static('static'))
  server.use(handle)

  router.get('*', (req, res) => {
    return handle(req, res)
  })

  server.listen(3001, (err) => {
    if (err) throw err
    console.log(`> Ready on http://localhost:3001${prefix}`)
  })
}).catch((e) => {
  console.log(e)
})