func GenerateJWT(username string) (string, error) {
	claims := jwt.RegisteredClaims{
		Subject:   username,
		ExpiresAt: jwt.NewNumericDate(time.Now().Add(2 * time.Hour)),
		IssuedAt:  jwt.NewNumericDate(time.Now()),
	}
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString([]byte("your-secret-key"))
}

func ValidateJWT(tokenStr string) (*jwt.RegisteredClaims, error) {
	token, err := jwt.ParseWithClaims(tokenStr, &jwt.RegisteredClaims{}, func(t *jwt.Token) (interface{}, error) {
		return []byte("your-secret-key"), nil
	})
	if err != nil || !token.Valid {
		return nil, err
	}
	claims, ok := token.Claims.(*jwt.RegisteredClaims)
	if !ok {
		return nil, errors.New("invalid claims")
	}
	return claims, nil
}