code: func Int64ValueOrDefault(r *http.Request, field string, def int64) (int64, error) {
  	if r.Form.Get(field) != "" {
  		value, err := strconv.ParseInt(r.Form.Get(field), 10, 64)
  		return value, err
  	}
  	return def, nil
  }
docs: // Int64ValueOrDefault parses a form value into an int64 type. If there is an
  // error, returns the error. If there is no value returns the default value.