code: func (p *peerConnection) BlockCapacity(targetRTT time.Duration) int {
  	p.lock.RLock()
  	defer p.lock.RUnlock()
  
  	return int(math.Min(1+math.Max(1, p.blockThroughput*float64(targetRTT)/float64(time.Second)), float64(MaxBlockFetch)))
  }
docs: // BlockCapacity retrieves the peers block download allowance based on its
  // previously discovered throughput.