Custom registration field that put you in a special usergroup?

[Goodman_2020]

Hello,

I would like to add a field in my register page, where you chose an option (between option 1 and option 2). If the user chose option 1, once i validate his registration, he is part of a usergroup1 (registered users) with his own permissions. If he chose optionn 2, he is registered in another usergroup that i will create, with other kind of permissions.

I know how to add a field to the registration page, but i don't know how to do the next steps, somebody could help me please?

Thanks