func ExponentialIntervalGenerator(rate float64) IntervalGenerator {
	rate = rate / float64(time.Second)
	return func(_ int64) int64 {
		return int64(rand.ExpFloat64() / rate)
	}
}
ExponentialIntervalGenerator creates an IntervalGenerator that outputs
exponentially distributed intervals. The resulting arrivals constitute
a Poisson process. The rate parameter is the average queries per second
for the generator, and corresponds to the reciprocal of the lambda parameter
to an exponential distribution. In English, if you want to generate 30 QPS
on average, pass 30 as the value of rate.
package bender
import (
	"math/rand"
	"time"
)