$ cd ~/.ssh/
$ touch config
$ vim config
and add the multiple keys to config:
# aaa account
Host github.com-aaa
HostName github.com
User git
IdentityFile ~/.ssh/id_rsa_aaa
# bbb account
Host github.com-bbb
HostName github.com
User git
IdentityFile ~/.ssh/id_rsa_bbb
git clone [email protected]:aaa/my_project.git my_project_aaa
As opsed to
git clone [email protected]:aaa/my_project.git my_project_default_git_user