CancellationToken

If handler implementation does blocking, long operations, or puts thread on sleep, then it should periodically check query.CancellationToken to test if service or request has been cancelled.

[Order(-1_000_000_000)]
class DelayQuery : IHandlerAsync
{
    public async Task HandleAsync<Request, Response>(IQuery<Request, Response> query) where Request : notnull
    {
        // Has cancel token
        if (query.CancellationToken.CanBeCanceled)
        {
            await Task.Delay(100, query.CancellationToken);
        }
        // Does not have a cancel token
        else
        {
            await Task.Delay(100);
        }
    }
}