// Save for subsequent use
	var hashedPayload string
	var md5Base64 string
	switch {
	case body == nil:
		hashedPayload = getSHA256Hash([]byte{})
	default:
		payloadBytes, err := io.ReadAll(body)
		if err != nil {
			return nil, err
		}
		hashedPayload = getSHA256Hash(payloadBytes)
		md5Base64 = getMD5HashBase64(payloadBytes)
	}
	// Seek back to beginning.
	if body != nil {
		body.Seek(0, 0)