func jitterUp(duration time.Duration, jitter float64) time.Duration {
	multiplier := jitter * (rand.Float64()*2 - 1)
	return time.Duration(float64(duration) * (1 + multiplier))
}
func jitterUp(duration time.Duration, jitter float64) time.Duration {
	multiplier := jitter * (rand.Float64()*2 - 1)
	return time.Duration(float64(duration) * (1 + multiplier))
}
// 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])
//
// Reference: https://godoc.org/github.com/grpc-ecosystem/go-grpc-middleware/util/backoffutils