return errors.New("Presign cannot be generated without access and secret keys")
	}

	// FIXME: Remove following portion of code after fixing a bug in minio-go preSignV2.

	d := UTCNow()
	// Find epoch expires when the request will expire.
	epochExpires := d.Unix() + expires

	// Add expires header if not present.
	expiresStr := req.Header.Get("Expires")
	if expiresStr == "" {