code: func (s *IssuesService) ListComments(ctx context.Context, owner string, repo string, number int, opt *IssueListCommentsOptions) ([]*IssueComment, *Response, error) {
  	var u string
  	if number == 0 {
  		u = fmt.Sprintf("repos/%v/%v/issues/comments", owner, repo)
  	} else {
  		u = fmt.Sprintf("repos/%v/%v/issues/%d/comments", owner, repo, number)
  	}
  	u, err := addOptions(u, opt)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	req, err := s.client.NewRequest("GET", u, nil)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	// TODO: remove custom Accept header when this API fully launches.
  	req.Header.Set("Accept", mediaTypeReactionsPreview)
  
  	var comments []*IssueComment
  	resp, err := s.client.Do(ctx, req, &comments)
  	if err != nil {
  		return nil, resp, err
  	}
  
  	return comments, resp, nil
  }
docs: // ListComments lists all comments on the specified issue. Specifying an issue
  // number of 0 will return all comments on all issues for the repository.
  //
  // GitHub API docs: https://developer.github.com/v3/issues/comments/#list-comments-on-an-issue