Usage :

yarn add envgrabber

in your app

const envGrabber = require('envgrabber');

(async () => {
  await envGrabber({
    bucketName: 'my_super_secret_bucket',
    fileName: '.env', // optional, '.env' is assumed.
  });
  console.log(process.env.MY_ENV_VAR);
})()

Authentication :

If the Storage bucket and your app are in the same project you won't need to do any authentications. If you'd like to use the module outside GAE, you'll have to make sure you've authenticated your local machine or started your app with the proper authentication environment variables.