server.js

const path = require('path');

const express = require('express');
const favicon = require('express-favicon');
const proxy = require('express-http-proxy');
const port = process.env.PORT || 8000;
const app = express();
app.use(favicon(__dirname + '/build/favicon.ico'));
// the __dirname is the current directory from where the script is running
app.use(express.static(__dirname));
app.use(express.static(path.join(__dirname, 'build')));

app.use(
  '/graphql',
  proxy('https://duo2-backend-staging.herokuapp.com', {
    proxyReqPathResolver: function(req) {
      return '/graphql';
    },
  })
);

app.get('/*', function(req, res) {
  res.sendFile(path.join(__dirname, 'build', 'index.html'));
});

app.use('/', proxy('https://duo2-backend-staging.herokuapp.com'));

app.listen(port);