code: func (p *pullMediatorImpl) Hello(dest string, nonce uint64) {
  	helloMsg := &proto.GossipMessage{
  		Channel: p.config.Channel,
  		Tag:     p.config.Tag,
  		Content: &proto.GossipMessage_Hello{
  			Hello: &proto.GossipHello{
  				Nonce:    nonce,
  				Metadata: nil,
  				MsgType:  p.config.MsgType,
  			},
  		},
  	}
  
  	p.logger.Debug("Sending", p.config.MsgType, "hello to", dest)
  	sMsg, err := helloMsg.NoopSign()
  	if err != nil {
  		p.logger.Errorf("Failed creating SignedGossipMessage: %+v", errors.WithStack(err))
  		return
  	}
  	p.Sndr.Send(sMsg, p.peersWithEndpoints(dest)...)
  }
docs: // Hello sends a hello message to initiate the protocol
  // and returns an NONCE that is expected to be returned
  // in the digest message.