code: func NewStorage(ctx context.Context, id StorageBackend, url *URL) (Storage, error) {
  	if be, found := storageRegistry[id]; found {
  		return be.New(ctx, url)
  	}
  	return nil, errors.Wrapf(ErrNotFound, "unknown backend: %s", url.String())
  }
docs: // NewStorage initializes a new storage backend.