Google Role Creation with Read Only Scopes
Step-1
Go to, https://admin.google.com > Admin Roles
Step-2
Click Create new Role.
Step-3
Define Role name and description.
Step-4
Choose API permission scopes,
Groups > Read
Users > Read
Step-5
Verify chosen roles and Click create role.
Step-6
Click Assign Role > Choose google service user.
Step-7
Confirm roles assigned and privileges.
Step-8
Go to API explorer, and Test assigned roles and privileges.
https://developers.google.com/admin-sdk/directory/v1/reference/groups/get
Enter your Google group mail address > Execute.
Make sure execution status 200.
Click Allow.