An interesting idea, but, I noticed some way down (almost the end in fact) that sadly the title is misleading. Yes you're using Golang, but, only as a "script". In reality, you're calling git command line to perform the actual "Back Up".

I had hoped to learn something new, about writing a git client in Golang, but even as a person that strongly believes in "Golang all the things", I'd do this in Bash scripting, and in much less time (and code).

I only skimmed the article, because it wasn't readily apparent to me what advantage all this code provides over using git (maybe with bash) to backup Github and GitLab repositories.

This seems like a very complicated alternative to git clone.