server.js

const { createServer } = require("http")
const { parse } = require("url")
const next = require("next")
const pathMatch = require("path-match")

const port = parseInt(process.env.PORT, 10) || 3000
const dev = process.env.NODE_ENV !== "production"
const app = next({ dev })
const handle = app.getRequestHandler()
const route = pathMatch()
const match = route("/category/:id")

app.prepare().then(() => {
  createServer((req, res) => {
    const { pathname, query } = parse(req.url, true)
    const params = match(pathname)
    if (params === false) {
      handle(req, res)
      return
    }
    // assigning `query` into the params means that we still
    // get the query string passed to our application
    // i.e. /category/foo?show-comments=true
    app.render(req, res, "/category", Object.assign(params, query))
  }).listen(port, err => {
    if (err) throw err
    console.log(`> Ready on http://localhost:${port}`)
  })
})