Dino Esposito explains plain direct claims-based authentication in ASP.NET Core.
Read this article in the September 2017 issue of MSDN Magazine
Great Article. In addtion to the post, use the below link to know how to migrate from 1.1. to 2.0 ASP.NET CORE based Identity framework updates and gotcha's:
https://docs.microsoft.com/en-us/aspnet/core/migration/1x-to-2x/identity-2x
In the last part of the article you had included the below lines, which seems to be relevant only for ASP.NET 1.1 version.
options.AutomaticChallenge = true, options.AuthenticationScheme = "Cookies",