code: func (arc *ConfigFactory) AddSource(source core.ConfigSource) error {
  	if source == nil {
  		return errors.New("source can not be nil")
  	}
  	if arc.initSuccess == false {
  		openlogging.Warn("Plz call factory.Init() first, failed to add source: " + source.GetSourceName())
  		return nil
  	}
  
  	return arc.configMgr.AddSource(source, source.GetPriority())
  }
docs: // AddSource return all values of different sources