using System;

using System.Text.Json;

using System.Text.Json.Serialization;

public class Program

{

    public static void Main()

    {

        string json = "{ \"access_token\": \"test-token\", \"expires_in\": 1234, \"refresh_token\": \"refresh\", \"scope\": \"identify\", \"token_type\": \"Bearer\" }";

        AccessTokenResponse response = JsonSerializer.Deserialize<AccessTokenResponse>(json);

        Console.WriteLine(response?.AccessToken);

    }

}

public class AccessTokenResponse

{

    [JsonPropertyName("access_token")] public string AccessToken { get; set; }

    [JsonPropertyName("expires_in")] public int ExpiresIn { get; set; }

    [JsonPropertyName("refresh_token")] public string RefreshToken { get; set; }

    [JsonPropertyName("scope")] public string Scope { get; set; }

    [JsonPropertyName("token_type")] public string TokenType { get; set; }

}