pkg/io/opener.go
func (o opener) Writer(ctx context.Context, path string) (io.WriteCloser, error) {
	g, err := o.openGCS(path)
	if err != nil {
		return nil, fmt.Errorf("bad gcs path: %v", err)
	}
	if g == nil {
		return os.Create(path)
	}
	return g.NewWriter(ctx), nil
}
func (o opener) Writer(ctx context.Context, path string) (io.WriteCloser, error) {
	g, err := o.openGCS(path)
	if err != nil {
		return nil, fmt.Errorf("bad gcs path: %v", err)
	}
	if g == nil {
		return os.Create(path)
	}
	return g.NewWriter(ctx), nil
}
// Writer returns a writer that overwrites the path.