exports.helloWorld = function helloWorld(req, res) {
  if (req.body.message === undefined) {
    res.status(400).send('No message defined!');
  } else {
    const zlib = require('zlib');

    // Obtain JSON stream from your source...

    res.writeHead(200, {
      'content-encoding': 'gzip',
    });

    json.pipe(zlib.createGzip()).pipe(res);
  }
};