server.js

const express = require('express');
const next = require('next');

// Import middleware.
const routes = require('./routes');

// Setup app.
const app = next({ dev: 'production' !== process.env.NODE_ENV });
const handle = app.getRequestHandler();
const handler = routes.getRequestHandler(app);

app.prepare()
  .then(() => {

    // Create server.
    const server = express();

    // Use our handler for requests.
    server.use(handler);

    // Don't remove. Important for the server to work. Default route.
    server.get('*', (req, res) => {
      return handle(req, res);
    });

    // Get current port.
    const port = process.env.PORT || 8080;

    // Error check.
    server.listen(port, err => {
      if (err) {
        throw err;
      }

      // Where we starting, yo!
      console.log(`> Ready on port ${port}...`);
    });
  });