code: func (nDB *NetworkDB) findCommonNetworks(nodeName string) []string {
  	nDB.RLock()
  	defer nDB.RUnlock()
  
  	var networks []string
  	for nid := range nDB.networks[nDB.config.NodeID] {
  		if n, ok := nDB.networks[nodeName][nid]; ok {
  			if !n.leaving {
  				networks = append(networks, nid)
  			}
  		}
  	}
  
  	return networks
  }
docs: // findCommonnetworks find the networks that both this node and the
  // passed node have joined.