How to login SSO (Single Sign On) with asp.net core?

How can i do a Single Sign On ? Step by step?Asp.net Core Any source Code Or Example not mvc example

i search many site but not proparly Explain.

user can login webapplication1.com then automatically login webaplication2.com not required agaain and again login

like user first time login in google no need to again login in youtube,gphoto,googledrive,map like that.