code: func (s *RepositoriesService) GetReleaseByTag(ctx context.Context, owner, repo, tag string) (*RepositoryRelease, *Response, error) {
  	u := fmt.Sprintf("repos/%s/%s/releases/tags/%s", owner, repo, tag)
  	return s.getSingleRelease(ctx, u)
  }
docs: // GetReleaseByTag fetches a release with the specified tag.
  //
  // GitHub API docs: https://developer.github.com/v3/repos/releases/#get-a-release-by-tag-name