code: func (sd *etcdServiceDiscovery) GetServers() []*Server {
  	ret := make([]*Server, 0)
  	sd.serverMapByID.Range(func(k, v interface{}) bool {
  		ret = append(ret, v.(*Server))
  		return true
  	})
  	return ret
  }
docs: // GetServers returns a slice with all the servers