static TimeSpan ExpDelay(int retryNumber) => Math.Pow(2, retryNumber).Apply(x => x * 1000) .Apply(x => x + Rnd.NextInt32(0, (int)(x / 3))) .Apply(TimeSpan.FromMilliseconds);
static Task <T> OnlinerDelay <T>(Task <T> task) => Delay(task, Rnd.NextInt32(2000, 5000));