code: func (srv *server) request(jsonData []byte, target string) ([]byte, error) {
  	result, err := srv.getResultMap(jsonData, target)
  	if err != nil {
  		return nil, err
  	}
  	cert := result["certificate"].(string)
  	if cert != "" {
  		return []byte(cert), nil
  	}
  
  	return nil, errors.Wrap(errors.APIClientError, errors.ClientHTTPError, stderr.New("response doesn't contain certificate."))
  }
docs: // request performs the common logic for Sign and Info, performing the actual
  // request and returning the resultant certificate.