You can add as many public:private key you want, the idea being to register them in %HOME%/.ssh/config file, in order for you to define remote with ssh addresses like:
workgh:Work
persgh:Personal
See “change github account mac command line” as an example of an ssh/config
file.
In your case:
#Personal GitHub
Host persgh
HostName github.com
User git
IdentityFile ~/.ssh/id_rsa_perso
#Personal Work
Host workgh
HostName github.com
User git
IdentityFile ~/.ssh/id_rsa_work
Reusing the same ssh key in different environment is genrally frowned upon.
See this SO question to generate multiple ssh keys non-interactively.