code: func NewDefaultCookieProtector() (CookieProtector, error) {
  	secret := make([]byte, cookieSecretSize)
  	if _, err := rand.Read(secret); err != nil {
  		return nil, err
  	}
  	return &DefaultCookieProtector{secret: secret}, nil
  }
docs: // NewDefaultCookieProtector creates a source for source address tokens