presign.go

// Presign signs a key object with an expiry time
func (s Service) Presign(key string) (string, error) {
	req, err := http.NewRequest(http.MethodGet, fmt.Sprintf("https://%s.s3.amazonaws.com/%s", s.Bucket, key), nil)
	if err != nil {
		return "", fmt.Errorf("s3.Presign.http.NewRequest(): %w", err)
	}

	// we sign the request with the signTime and a time expiration of 1 day
	_, err = s.Signer.Presign(req, nil, "s3", *s.Session.Config.Region, time.Hour*24, getSignTime())
	if err != nil {
		return "", fmt.Errorf("s3.Presign.v4.NewSigner(): %w", err)
	}

	return req.URL.String(), nil
}

// getSignTime returns a truncated time to day precision
// with this precision, will get the same signature during the day
func getSignTime() time.Time {
	return time.Now().Truncate(time.Hour * 24).UTC()
}