code: func (m *Meter) StartTransfer(name string) {
  	if m == nil {
  		return
  	}
  
  	defer m.update(false)
  	idx := atomic.AddInt64(&m.transferringFiles, 1)
  	m.fileIndexMutex.Lock()
  	m.fileIndex[name] = idx
  	m.fileIndexMutex.Unlock()
  }
docs: // StartTransfer tells the progress meter that a transferring file is being
  // added to the TransferQueue.