code: func (api *API) RailgunZones(railgunID string) ([]Zone, error) {
  	uri := api.userBaseURL("") + "/railguns/" + railgunID + "/zones"
  	res, err := api.makeRequest("GET", uri, nil)
  	if err != nil {
  		return nil, errors.Wrap(err, errMakeRequestError)
  	}
  	var r ZonesResponse
  	if err := json.Unmarshal(res, &r); err != nil {
  		return nil, errors.Wrap(err, errUnmarshalError)
  	}
  	return r.Result, nil
  }
docs: // RailgunZones returns the zones that are currently using a Railgun.
  //
  // API reference: https://api.cloudflare.com/#railgun-get-zones-connected-to-a-railgun