react-hot-reloader with custom server proxying to webpack-dev-server

server.js

const express = require('express');
const url = require('url');
const path = require('path');

const app = express();

if (process.env.NODE_ENV !== 'production') {
  app.use('/assets', require('proxy-middleware')(url.parse('http://localhost:8080/assets')));
} else {
  app.use('/assets', express.static(path.resolve(__dirname, '../www/assets')));
}

app.get('/', (req, res) => {
  res.sendFile(path.resolve(__dirname, '../www/index.html'));
});

app.listen(3000, () => console.log('Server listening on port 3000'));