code: func (r *RateLimiter) UpdateBandwidth(bandwidth float64) {
  	r.lock.Lock()
  	defer r.lock.Unlock()
  	//  Convert bandwidth from bytes/second to bytes/nanosecond
  	b := bandwidth / float64(time.Second)
  	r.bandwidth = b
  	//  Reset allowance
  	r.allowance = 0
  	r.maxAllowance = bandwidth
  	r.lastUpdate = time.Now()
  }
docs: //  Changes bandwidth of a RateLimiter and resets its allowance