challenge

type Config struct {
	// Secret is the site's Turnstile secret key; required.
	Secret string
	// Timeout bounds one verification; 10 seconds when zero.
	Timeout time.Duration
	// URL is the verification endpoint; SiteVerifyURL when empty.
	URL string
}

type Service interface {
	// Verify reports whether token is a valid Turnstile response issued to
	// the client at ip. An error means the verification could not be done.
	Verify(ctx context.Context, token string, ip string) (bool, error)
}