code: func NewCatalogServicesQuery(s string) (*CatalogServicesQuery, error) {
  	if !CatalogServicesQueryRe.MatchString(s) {
  		return nil, fmt.Errorf("catalog.services: invalid format: %q", s)
  	}
  
  	m := regexpMatch(CatalogServicesQueryRe, s)
  	return &CatalogServicesQuery{
  		stopCh: make(chan struct{}, 1),
  		dc:     m["dc"],
  	}, nil
  }
docs: // NewCatalogServicesQuery parses a string of the format @dc.