I've not used Github a lot anymore in recent times because we've switched to Gitlab some time ago. The main reason for using Github at this point is client work. But sometimes, I still need my account for open source reasons.

For one of the customers I do work for, however, I was asked to create a separate Github account. Now I was running into some issues because the private repositories are now shared with this new account, but by default I'm logged into my own account on the commandline (well, it picks my default key). Searching around I ended up on the site of freeCodeCamp, where Bivil M Jacob shared the solution that ended up working. The solution: Add a configuration file.

The first three steps are pretty standard and now that hard to understand, but the fourth step was new to me. I had no idea this was possible. So I followed the guidance of Bivil and ended up with my own .ssh/config file:

# Skoop, - the default config
Host github.com
   HostName github.com
   User git
   IdentityFile ~/.ssh/id_rsa

# clientskoop
Host client.github.com    
   HostName github.com
   User git
   IdentityFile ~/.ssh/cf_ed25519

I've redacted this example to not include my actual client name. Now, if I want to clone a private repository from my client, all I need to do is:

git clone git@client.github.com:clientname/clientrepo.git

In the above command, note the client.github.com host name that is the same as the Host I defined in the config file. And lo and behold, when I clone in this way I can clone without a problem. It takes the correct key for this specific repository and I can do everything I want: push, pull, etc.

Sometimes the solution is simpler than you would've imagined.