code: func (s *VenueService) Categories() ([]Category, *http.Response, error) {
  	cats := new(categoriesResp)
  	response := new(Response)
  	resp, err := s.sling.New().Get("categories").Receive(response, response)
  
  	if err == nil {
  		json.Unmarshal(response.Response, cats)
  	}
  
  	return cats.Categories, resp, relevantError(err, *response)
  }
docs: // Categories returns a hierarchical list of categories applied to venues.
  // https://developer.foursquare.com/docs/api/venues/categories