CancellatioToken interface

public class CancellationChangeToken : IChangeToken
{
   // 1. It holds a private reference to your token
   private readonly CancellationToken _token;
   public CancellationChangeToken(CancellationToken token)
   {
       _token = token;
   }
   // 2. The wrapper's "HasChanged" property just checks your token
   public bool HasChanged => _token.IsCancellationRequested;
   // 3. It tells the Cache how to listen for the "Cancel" event
   public IDisposable RegisterChangeCallback(Action<object> callback, object state)
   {
       // It simply hooks into the standard CancellationToken.Register method
       return _token.Register(callback, state);
   }
   
   // Most change tokens aren't active by default, but this one is
   public bool ActiveChangeCallbacks => true;
}