if err != nil {
		return nil, err
	}

	// Set form content-type.
	req.Header.Set("Content-Type", w.FormDataContentType())
	return req, nil
}

func buildGenericPolicy(t time.Time, accessKey, region, bucketName, objectName string, contentLengthRange bool) []byte {
	// Expire the request five minutes from now.
	expirationTime := t.Add(time.Minute * 5)