code: func (c *Controller) NotFound(msg string, objs ...interface{}) Result {
  	finalText := msg
  	if len(objs) > 0 {
  		finalText = fmt.Sprintf(msg, objs...)
  	}
  	c.Response.Status = http.StatusNotFound
  	return c.RenderError(&Error{
  		Title:       "Not Found",
  		Description: finalText,
  	})
  }
docs: // NotFound returns an HTTP 404 Not Found response whose body is the
  // formatted string of msg and objs.