code: func (c *Conn) UpdateSetting(args map[string]interface{}, filter_indices ...string) (ClusterStateResponse, error) {
  	var url string
  	var retval ClusterStateResponse
  
  	url = "/_cluster/state"
  
  	body, err := c.DoCommand("GET", url, args, nil)
  	if err != nil {
  		return retval, err
  	}
  	if err == nil {
  		// marshall into json
  		jsonErr := json.Unmarshal(body, &retval)
  		if jsonErr != nil {
  			return retval, jsonErr
  		}
  	}
  	return retval, err
  }
docs: // State gets the comprehensive state information for the whole cluster
  // see http://www.elasticsearch.org/guide/reference/api/admin-cluster-state/