code: func (c *Client) AddTxtRecord(zoneName string, fqdn, value string, ttl int) error {
  	host := dns01.UnFqdn(strings.TrimSuffix(dns01.UnFqdn(fqdn), zoneName))
  
  	reqURL := *c.BaseURL
  	reqURL.Path += "add-record.json"
  
  	q := reqURL.Query()
  	q.Add("domain-name", zoneName)
  	q.Add("host", host)
  	q.Add("record", value)
  	q.Add("ttl", strconv.Itoa(ttlRounder(ttl)))
  	q.Add("record-type", "TXT")
  	reqURL.RawQuery = q.Encode()
  
  	raw, err := c.doRequest(http.MethodPost, &reqURL)
  	if err != nil {
  		return err
  	}
  
  	resp := apiResponse{}
  	if err = json.Unmarshal(raw, &resp); err != nil {
  		return fmt.Errorf("apiResponse unmarshaling error: %v: %s", err, string(raw))
  	}
  
  	if resp.Status != "Success" {
  		return fmt.Errorf("fail to add TXT record: %s %s", resp.Status, resp.StatusDescription)
  	}
  
  	return nil
  }
docs: // AddTxtRecord add a TXT record