Gitlab git client shutdown if unused for too long

I am using the official docker version of Gitlab. When the git client is not used for too long, I obtain the following error message for the git fetch command:

GitLab: API is not accessible
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

After I log into my Gitlab web account, the git client wake up and the git fetch works again.
How can I enforce the git client to be always operational?