server.js

const {join} = require('path')
const {createServer} = require('http')
const next = require('next')

const app = next({dev: process.env.NODE_ENV !== 'production'})
const handle = app.getRequestHandler()
const port = Number.parseInt(process.argv.pop().split('=')[1] || 9000)
const root = process.cwd()

app.prepare().then(() => {
  createServer((req, res) => {
    if (req.url.startsWith('/static/')) {
      if (req.url.endsWith('/sw.js')) {
        res.setHeader('Service-Worker-Allowed', '/')
      }
      app.serveStatic(req, res, join(root, `.${req.url}`))
    } else {
      handle(req, res, req.url)
    }
  }).listen(port, err => {
    if (err) {
      throw err
    }
    console.log(`> Ready on http://localhost:${port}`)
  })
})