code: func (c *Client) Markdown(ctx context.Context, text string, opt *MarkdownOptions) (string, *Response, error) {
  	request := &markdownRequest{Text: String(text)}
  	if opt != nil {
  		if opt.Mode != "" {
  			request.Mode = String(opt.Mode)
  		}
  		if opt.Context != "" {
  			request.Context = String(opt.Context)
  		}
  	}
  
  	req, err := c.NewRequest("POST", "markdown", request)
  	if err != nil {
  		return "", nil, err
  	}
  
  	buf := new(bytes.Buffer)
  	resp, err := c.Do(ctx, req, buf)
  	if err != nil {
  		return "", resp, err
  	}
  
  	return buf.String(), resp, nil
  }
docs: // Markdown renders an arbitrary Markdown document.
  //
  // GitHub API docs: https://developer.github.com/v3/markdown/