Private repo on Github

Hello all :slight_smile:,
A small Github question if you may.
I have a repo on Github with a plugin for Discourse. This repo is private.
I would like to insert it into the yml file but because the repo is private, it can’t clone it.
I’m familiar with the workaround of adding the user-name and the password but I prefer not to do it. I was wondering if it’s possible to use the SSH keys (and not the password) that I already setup for the theme, or new ones.
Have someone faced with similar situation?
Thank you :slight_smile: