How I use multiple ssh keys for different users with git and vscode
Where <HOST> is usually gh_ to easily identify that it is for that GitHub user.
Host <HOST>
HostName github.com
IdentityFile ~/.ssh/<SSH KEY FILE>
Where <HOST> is the same as the previous.
[url "git@<HOST>:<USERNAME>"]
insteadOf = https://github.com/<USERNAME>
NOTE!
This has to be repeated for every orginization this user is part of.