code: func NewTokenBucketRateLimiterWithClock(qps float32, burst int, c Clock) RateLimiter {
  	limiter := rate.NewLimiter(rate.Limit(qps), burst)
  	return newTokenBucketRateLimiter(limiter, c, qps)
  }
docs: // NewTokenBucketRateLimiterWithClock is identical to NewTokenBucketRateLimiter
  // but allows an injectable clock, for testing.