code: func (s *RepositoriesService) CreateComment(ctx context.Context, owner, repo, sha string, comment *RepositoryComment) (*RepositoryComment, *Response, error) {
  	u := fmt.Sprintf("repos/%v/%v/commits/%v/comments", owner, repo, sha)
  	req, err := s.client.NewRequest("POST", u, comment)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	c := new(RepositoryComment)
  	resp, err := s.client.Do(ctx, req, c)
  	if err != nil {
  		return nil, resp, err
  	}
  
  	return c, resp, nil
  }
docs: // CreateComment creates a comment for the given commit.
  // Note: GitHub allows for comments to be created for non-existing files and positions.
  //
  // GitHub API docs: https://developer.github.com/v3/repos/comments/#create-a-commit-comment