How to enable automatic logoff after 5 minutes?

Nextcloud version 16.0.1
Operating system and version Ubuntu 18.4
nginx version 1.15.8
PHP version 7.3

I don’t have an issue, but I have a question.
I’d like to change the session lifetime to 5 minutes?
So after being logged on it should log you out after five minutes of inactivity.

I found something by googleling called “session_keepalive”, but I don’t know where to find this (it’s not in my config.php) and how to set it up.

Perhaps someone can give me some directions.