JSON.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Networking;

public class LoadJson : MonoBehaviour
{

    // Use this for initialization
    IEnumerator Start()
    {
        var www = UnityWebRequest.Get("file://" + Application.streamingAssetsPath + "/demo.json");

        yield return www.SendWebRequest();

        Debug.Log(www.downloadHandler.text);

        var demo = JsonUtility.FromJson<Demo>(www.downloadHandler.text);

        Debug.Log(demo.Id);
        Debug.Log(demo.UserName);
    }

    // Update is called once per frame
    void Update()
    {


    }
}

[System.Serializable]
public class Demo
{
    public int Id;
    // public string UserID { get; set; }
    public string UserName;
    // public string LoginType { get; set; }
    // public string email { get; set; }
    // public int Coin { get; set; }
    // public string GameNoryaKey { get; set; }
}