Multiple SSH Keys for different Github Accounts

Assuming you have different ssh keys you need to use because you have multiple github accounts or different keys for different repos, you can add multiple configurations to ~/.ssh/config.

All keys should be already added to the ssh-agent using ssh-add ~/.ssh/key (use -K in macOS).

In ~/.ssh/config:

Host example1
    HostName github.com
    User git
    IdentityFile ~/.ssh/a_key

Host example2
    HostName github.com
    User git
    IdentityFile ~/.ssh/another_key

Also, make sure the origin remote in .git/config uses the Host defined ~/.ssh/config.

For example, for the example1 entry:

[remote "origin"]
    url = git@example1:account/project.git