I have a thread with a more comprehensive description of the problem at https://moodle.org/mod/forum/discuss.php?d=355492#p1434007. But what I said there is:
I went to Plugins -> Authentication -> Manage authentication,
disabled OAuth2 (googleoauth2) and enabled OAuth 2 (oauth2). Then I went
to Plugins overview, only to find there is no uninstall option for the googleoauth2 module.
So I moved
auth/googleoauth2 out of the way by renaming it - after all, it was disabled. Refreshing the Plugins overview page
got Moodle to complain that the plugin could not be found on the disk,
followed by an option to update the database - so I did that, and thought I'd got googleoauth2 uninstalled.
out, then tried to log back in using the core OAuth2 Google button and was
taken to the Google account chooser, only to then get a BIG message that
googleoauth2 could not be found, and no way of getting the site to
load. (From memory, it was trying to invoke /auth/googleoauth2/google_redirect.php.)
I'm guessing that there's no uninstall option for googleoauth2 because I have around 80 users who registered through it and are using it. I can't delete their accounts - they're active users with stuff going on in courses - and even if there was
an uninstall option, I'd be reluctant to mess with it unless I was confident that a) the uninstall wouldn't mess with their accounts and b) that the uninstall would also resolve the problem with sessions timing out after 30 - 90 seconds.
I suspect that I'm going to have to:
- enable the core oauth2 module
- disable googleoauth2
- purge all cached session data on the server
- rename the auth/googleoauth2 directory
- update the plugins database
- log out of Google completely, on all my machines, and
- delete all cookies in the browser
in order to get this resolved. Then the question is, are my users going to have to go through a similar process of logging out and deleting cookies?
In any case, I can't try this until things go quiet on the server, some time early next week.