code: func (cm *ClientManager) SubscribeTotalCapacity(ch chan uint64) uint64 {
  	cm.lock.Lock()
  	defer cm.lock.Unlock()
  
  	cm.totalCapacityCh = ch
  	return uint64(cm.totalCapacity)
  }
docs: // SubscribeTotalCapacity returns all future updates to the total capacity value
  // through a channel and also returns the current value