Accessing current user data outside the controller

I`m trying to add to my ASP.NET Core project some sort of audit data like in http://benjii.me/2014/03/track-created-and-modified-fields-automatically-with-entity-framework-code-first/ (update data about user and time in overrided SaveChangesAsync method) However I can`t get the current user Id. I`ve tried using HttpCeontextAccessor, but it is always null. How to get user Id in such scenario?