code: func (whisper *Whisper) Start(*p2p.Server) error {
  	log.Info("started whisper v." + ProtocolVersionStr)
  	go whisper.update()
  
  	numCPU := runtime.NumCPU()
  	for i := 0; i < numCPU; i++ {
  		go whisper.processQueue()
  	}
  
  	return nil
  }
docs: // Start implements node.Service, starting the background data propagation thread
  // of the Whisper protocol.