How to set a displayname for IdentityServer4 when using external provider

I've set up our IS4 Server with google. Everything is working for login. Now there is an issue that I just can't seem to resolve. When using google it provides me the username as a number. Which is as expected. How do I get a proper Display Name for when the user is logged in? what is the proper approach? Right now I am using IdentityServer4.Extensions.PrincipalExtensions.GetDisplayName() to display the name and it is showing the GoogleId