Get an OAuth client ID for your app
Build a standalone app and download the apk, or find one that you have already built.
Go to the Google Developer Credentials.
Click Create credentials, then OAuth client ID, then select the Android radio button.
Run expo fetch:android:hashes.
Take Google Certificate Fingerprint from previous step and insert it in the Signing-certificate fingerprint field.
Add your android.package from app.json (eg: ca.brentvatne.growlerprowler) to the Package name field.
Press Create.