Read and Write data to a private Google Sheet with an OAuth2 (not async)

GoogleSheetsOAuth2.cs

using System.IO;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Services;
using Google.Apis.Sheets.v4;
using Google.Apis.Sheets.v4.Data;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;

namespace Rovsau.Unity.Google
{
    public class GoogleSheetsOAuth2 : MonoBehaviour
    {
        // From console.cloud.google.com > Left Menu > APIs and services > Credentials > (Select Service Account) > Keys >  Add Key > JSON.
        // Relative path to the file.
        private const string jsonKeyFile = "secrets.json";

        // From sheet URL.
        private const string sheetID = "11raBG5B9CKcHOOfg0jUwfRuGQ5Zbswi3dDpcsciKzad";

        // Worksheet!Range like Sheet1!A1:X4
        private const string readRange = "Output!1:1";
        private const string writeRange = "Output!4:4";


        [InitializeOnLoadMethod]
        public static void Example()
        {
            string json = Path.Combine(Path.GetDirectoryName(Application.dataPath), jsonKeyFile);
            SheetsService sheetsService = GetSheetsService(json, "My OAuth2 Example");

            // Since these methods are async, but our execution is parallel, the output will come in the opposite order.
            // WriteSheetData will finish before ReadSheetData. 
            ReadSheetData(sheetsService, sheetID, readRange);

            List<IList<object>> inputdata = new List<IList<object>>();
            inputdata.Add(new List<object> { "This", "is", "my", "input" });

            WriteSheetData(sheetsService, sheetID, writeRange, inputdata);
        }

        public static SheetsService GetSheetsService(string jsonKeyFilePath, string applicationName)
        {
            GoogleCredential credential = GoogleCredential.FromFile(jsonKeyFilePath).CreateScoped(SheetsService.Scope.Spreadsheets);
            return new SheetsService(new BaseClientService.Initializer
            {
                HttpClientInitializer = credential,
                ApplicationName = applicationName
            });
        }

        private static void ReadSheetData(SheetsService sheetsService, string sheetID, string sheetRange)
        {
            SpreadsheetsResource.ValuesResource.GetRequest request = sheetsService.Spreadsheets.Values.Get(sheetID, sheetRange);

            request.ExecuteAsync().ContinueWith(response =>
            {
                if (response.IsFaulted)
                {
                    Debug.LogError("Failed to read Google Sheet data: " + response.Exception);
                    return;
                }

                ValueRange result = response.Result;
                if (result != null && result.Values != null)
                {
                    foreach (IList<object> row in result.Values)
                    {
                        Debug.Log(string.Join(", ", row));
                    }
                }
                else
                {
                    Debug.LogWarning("No data found in the Google Sheet.");
                }
            });
        }

        public static void WriteSheetData(SheetsService sheetsService, string sheetID, string sheetRange, List<IList<object>> data)
        {
            ValueRange valueRange = new ValueRange
            {
                Range = sheetRange,
                Values = data
            };

            SpreadsheetsResource.ValuesResource.UpdateRequest request = sheetsService.Spreadsheets.Values.Update(valueRange, sheetID, sheetRange);

            request.ValueInputOption = SpreadsheetsResource.ValuesResource.UpdateRequest.ValueInputOptionEnum.RAW;

            UpdateValuesResponse response = request.Execute();

            Debug.Log("Updated " + response.UpdatedCells + " cells in the Google Sheet");
        }
    }
}

Alternate WriteSheetData (not a real async solution)

public static void WriteSheetData(SheetsService sheetsService, string sheetID, string sheetRange, List<IList<object>> data)
{
    ValueRange valueRange = new ValueRange
    {
        Range = sheetRange,
        Values = data
    };

    SpreadsheetsResource.ValuesResource.UpdateRequest request = sheetsService.Spreadsheets.Values.Update(valueRange, sheetID, sheetRange);

    request.ValueInputOption = SpreadsheetsResource.ValuesResource.UpdateRequest.ValueInputOptionEnum.RAW;

    request.ExecuteAsync().ContinueWith(response =>
    {
        if (response.IsFaulted)//
        {
            Debug.LogError("Failed to update Google Sheet data: " + response.Exception);
        }
        Debug.Log("Updated " + response.Result.UpdatedCells + " cells in the Google Sheet");
    });
}