WaitSlowTask.cs

public static class TaskExtensions
{

    public static async Task WaitSlowTask(this Task waitTask, TimeSpan slowTime, Action slowAction)
    {
        var taskCompleted = new CancellationTokenSource();
        if (slowAction != null)
        {
            _ = Task.Delay(slowTime, taskCompleted.Token).ContinueWith(_ => slowAction.Invoke(), TaskContinuationOptions.OnlyOnRanToCompletion);
        }
        await waitTask.ConfigureAwait(false);
        taskCompleted.Cancel();
    }
}