func ExponentBase2(a uint) uint
ExponentBase2 computes 2^(a-1) where a >= 1. If a is 0, the result is 0.
func JitterUp(duration time.Duration, jitter float64) time.Duration
JitterUp adds random jitter to the duration.
This adds or subtracts time from the duration within a given jitter fraction. For example for 10s and jitter 0.1, it will return a time within [9s, 11s])