code: func (c *Client) GetDomainName() (string, error) {
  	out, err := c.Get(c.Endpoint("domain"), url.Values{})
  	if err != nil {
  		return "", trace.Wrap(err)
  	}
  	var domain string
  	if err := json.Unmarshal(out.Bytes(), &domain); err != nil {
  		return "", trace.Wrap(err)
  	}
  	return domain, nil
  }
docs: // GetDomainName returns local auth domain of the current auth server