signature is invalid ketika cek token di Gin

Hallo, saya mau bertanya. disini saya punya error signature is invalid ketika cek token JWT dengan bahasa golang di framework GIN.

kira2 apa ya solusinya ?

terima kasih

var JWT_SECRET = "SECRET-KEY"

// base64.URLEncoding.DecodeString(JWT_SECRET)
func IsAuth() gin.HandlerFunc {
    log.Print("bro ", CheckJWT())
    return CheckJWT()
}

func CheckJWT() gin.HandlerFunc {
    return func(c *gin.Context) {
        log.Print("cuk ", JWT_SECRET)
        authHeader := c.Request.Header.Get("Authorization")
        bearerToken := strings.Split(authHeader, " ")
        // log.Print("ini ", bearerToken)
        token, err := jwt.Parse(bearerToken[1], func(token *jwt.Token) (interface{}, error) {
            // Don't forget to validate the alg is what you expect:
            if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
                return nil, fmt.Errorf("Unexpected signing method: %v", token.Header["alg"])
            }

            // hmacSampleSecret is a []byte containing your secret, e.g. []byte("my_secret_key")
            return []byte(JWT_SECRET), nil
        })

        if claims, ok := token.Claims.(jwt.MapClaims); ok && token.Valid {
            fmt.Println(claims["foo"], claims["nbf"])
        } else {
            log.Print("err ", err)
            c.JSON(422, gin.H{
                "msg":   " Invalid Token",
                "error": err})
            c.Abort()
            return
        }
    }
}