code: function html(req, res) {
    fs.readFile(path.join(__dirname, 'index.html'), function read(err, file) {
      if (err) throw err;
  
      res.setHeader('Content-Length', file.length);
      res.writeHead(200, { 'Content-Type': 'text/html' });
  
      res.end(file);
    });
  }
docs: Serve the index.html
  
  @param {Request} req HTTP request.
  @param {Response} res HTTP response.
  @private