This release brings some (minor) breaking changes to the public API. First, we added a non-generic overload to Send on IMediator:

public interface IMediator  
{
    Task<TResponse> Send<TResponse>(IRequest<TResponse> request, CancellationToken cancellationToken = default);

+   Task<object> Send(object request, CancellationToken cancellationToken = default);

    Task Publish(object notification, CancellationToken cancellationToken = default);

    Task Publish<TNotification>(TNotification notification, CancellationToken cancellationToken = default)
        where TNotification : INotification;
}

Second, we've modified the Mediator class to include the CancellationToken for the virtual PublishCore method that allows implementors to override the publishing strategy and accept the notification itself:

-        protected virtual async Task PublishCore(IEnumerable<Func<Task>> allHandlers)
+        protected virtual async Task PublishCore(IEnumerable<Func<INotification, CancellationToken, Task>> allHandlers, INotification notification, CancellationToken cancellationToken)
         {
             foreach (var handler in allHandlers)
             {
-                await handler().ConfigureAwait(false);
+                await handler(notification, cancellationToken).ConfigureAwait(false);
             }
         }

Finally, a new feature! We've added some new built-in pipeline behaviors for handling exceptions. You can now handle specific exceptions (similar to an Exception Filter in ASP.NET Core):

public interface IRequestExceptionHandler<in TRequest, TResponse, TException>  
    where TException : Exception
{
    Task Handle(TRequest request, 
        TException exception, 
        RequestExceptionHandlerState<TResponse> state, 
        CancellationToken cancellationToken);
}

Alternatively, if you don't want to provide alternate responses based on exceptions, you can provide exception actions:

public interface IRequestExceptionAction<in TRequest, in TException>  
    where TException : Exception
{
    Task Execute(TRequest request, TException exception, CancellationToken cancellationToken);
}

These are a bit simpler if you want to just provide some exception logging. I've also updated the MS DI Extensions package, which registers these new behaviors and interfaces. Enjoy!