Sessions are not cleaned up when using bolt db

[maragunde93]

Is this a bug report or feature request?

• Bug Report

Describe the bug

We have and old version of oidc-authservice but I still think this bug happens on the current version, please read through it.

We faced multiple disruptions because of the bolt db size keeps increasing, as these are sessions that expires one would expect that the size of it is kind of constant.

When I started checking the code I saw that there is a process that should clean the sessions, I keep debuging this and realized that some data of the sessions had an expiratio date after 60 years from now. Finally after a lot of troubleshooting and debugging I found that this line is wrong (at least for my tests I am not an expert on go): https://github.com/arrikto/oidc-authservice/blob/master/sessions/state.go#L52

time.minute is a constant that returns 1 minute in nano seconds:

As the MaxAge is expected to be in seconds the result is totally different from 20 minutes.

How to Reproduce
Save sessions on bolt db
verify the expiration date of the sessions

Expected behavior

Sessions should be cleaned up