code: func (eg *EngineGroup) Close() error {
  	err := eg.Engine.Close()
  	if err != nil {
  		return err
  	}
  
  	for i := 0; i < len(eg.slaves); i++ {
  		err := eg.slaves[i].Close()
  		if err != nil {
  			return err
  		}
  	}
  	return nil
  }
docs: // Close the engine