Itunesconnect api JWT problem

Hey, I'm trying to use https://developer.apple.com/documentation/appstoreconnectapi/

Heres the code to generete JWT token:

func main() {

  bytes, err := ioutil.ReadFile("AuthKey.p8")
  if err!=nil {
  fmt.Println(err)
  }

  block, _ := pem.Decode(bytes)
  key, err := x509.ParsePKCS8PrivateKey(block.Bytes)
  if err != nil {
  log.Fatal(err)
  }

  token := jwt.NewWithClaims(jwt.SigningMethodES256, jwt.MapClaims{
  "iss": iss,
  "exp": time.Now().Unix()+6000,
  "aud": "appstoreconnect-v1",
  })

  token.Header["kid"] = kid

  tokenString, err := token.SignedString(key)
  if err != nil {
  log.Fatal(err)
  }
  fmt.Println(tokenString)

}

I'm getting the JWT code but when I'm trying to use it got 401 NOT_AUTHORIZED