docs: func NewCookieSigner(keyID string, privKey *rsa.PrivateKey, opts ...func(*CookieOptions)) *CookieSigner {
  	signer := &CookieSigner{
  		keyID:   keyID,
  		privKey: privKey,
  		Opts:    CookieOptions{}.apply(opts...),
  	}
  
  	return signer
  }