This question already has an answer here:
My student Gmail account that I used to create my Pokemon Go account is going to expire.
Is there any way I can get Pokemon Go to accept another Gmail account?
Someone commented to a similar post before, Does this work? :
Note an anonymous user says: Deleting the college email doesn’t delete the Google account…go too accounts.google.com and change the email used to login where it says “Login options” (or something similar) Same Google account, different login info – Dragonrage Aug 4 at 16:31
Actually, I am focused on whether I could go to Google and change my username like the above email mentioned and log into Pokemon Go with my new username.