Firebase: How to get the Google signing Email before the sign in as a firebase user Using Google Auth

I need to Get Email when Google Auth Provider Runing . but Before the sign in Or Sign Up to firebase . Because I need to Limit Signin only for Specified Domains (ex:desh@djhub.biz) i need to set up signin only for this domain users (@djhub.biz). But Its Need To Check Before This Method . This Is the Final Method