Use a PEM file to pull or push
You can use your server .pem file instead of creating a new key pair.
Get your .pem public key, by running the following command:
$ ssh-keygen -y -f KEYFILE
Add this key to Gitlab using the application API.
Edit (or create if not exists) ~/.ssh/config and add the following lines, replacing SERVER-IP with the IP address or domain name of the GitLab server if necessary and KEYFILE with the full path to the .pem file.
Host SERVER-IP IdentityFile KEYFILE