code: func (s *IssueService) DownloadAttachment(attachmentID string) (*Response, error) {
  	apiEndpoint := fmt.Sprintf("secure/attachment/%s/", attachmentID)
  	req, err := s.client.NewRequest("GET", apiEndpoint, nil)
  	if err != nil {
  		return nil, err
  	}
  
  	resp, err := s.client.Do(req, nil)
  	if err != nil {
  		jerr := NewJiraError(resp, err)
  		return resp, jerr
  	}
  
  	return resp, nil
  }
docs: // DownloadAttachment returns a Response of an attachment for a given attachmentID.
  // The attachment is in the Response.Body of the response.
  // This is an io.ReadCloser.
  // The caller should close the resp.Body.