Today Google updated Google Drive on iOS with a feature called Privacy Screen. It lets you lock the app with Face ID and Touch ID. Digital Trends notes:
The feature is activated each time you close the Drive app and reopen it and also locks files if you switch between Google Drive and another app, according to a Google spokesperson. You’ll have the option to turn this feature on and adjust its timing in Drive settings.
I personally would like Apple to let us lock every app with Face ID / Touch ID. Apps can clearly do this by themselves, but having it “baked” into the operating system is ideal.
App Store: Google Drive – Free