next.js/examples/root-static-files/server.js

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

const port = parseInt(process.env.PORT, 10) || 3000
const dev = process.env.NODE_ENV !== 'production'
const app = next({ dev })
const handle = app.getRequestHandler()

app.prepare().then(() => {
  createServer((req, res) => {
    const parsedUrl = parse(req.url, true)
    const rootStaticFiles = ['/robots.txt', '/sitemap.xml', '/favicon.ico']
    if (rootStaticFiles.indexOf(parsedUrl.pathname) > -1) {
      const path = join(__dirname, 'static', parsedUrl.pathname)
      app.serveStatic(req, res, path)
    } else {
      handle(req, res, parsedUrl)
    }
  }).listen(port, err => {
    if (err) throw err
    console.log(`> Ready on http://localhost:${port}`)
  })
})