Notes

[tlhunter]

README should note that the download method is a promsie:

Downloader
  .download('[Google Drive FileID]', 'output.xlsx', 'client_secret.json')
  .then(data => {
  });

What does the contents of client_secret.json look like? I think it would make more sense to provide as a string instead of a path for the third argument.

The mandatory 250ms is very scary. Do you know what causes it? Does the time increase or decrease depending on CPU or bandwidth?