Session Maintain

Question

I have a project where multiple domains are running for single project means all domain have same A record mapped and we have hosted project on IIS. And it's working fine, but I want to use same session if use switch from www.abc.com to www.xyz.com ( we have 1000 different domains) he doesn't need to login again as its part of same project.

 

I am already tired but does not get any proper solution

 

Please suggest the best way. Please don't suggest post message. We are using ASP.NET Core MVC.