server.js

const { createServer } = require('http');
const { parse } = require('url');
const next = require('next');
const pathMatch = require('path-match');
const opn = require('opn');
const getPort = require('get-port');

const dev = process.env.NODE_ENV !== 'production';
const app = next({ dev });
const handle = app.getRequestHandler();
const route = pathMatch();
const match = route('/learn/:id');

getPort({ port: 3000 }).then(port => {
  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. /blog/foo?show-comments=true
      app.render(req, res, '/learn/subject', Object.assign(params, query));
    }).listen(port, err => {
      if (err) throw err;
      console.log(`>> App running on http://localhost:${port}`);
      opn(`http://localhost:${port}`);
    });
  });
});