code: func (r *Regexp) Values(s string) url.Values {
  	match := r.compiled.FindStringSubmatch(s)
  	if match != nil {
  		values := url.Values{}
  		for k, v := range r.groups {
  			values.Add(v, match[r.indices[k]])
  		}
  		return values
  	}
  	return nil
  }
docs: // Values matches the regexp and returns the results for positional and
  // named groups. Positional values are stored using an empty string as key.
  // If the string doesn't match it returns nil.