Winappdriver unit test c# automation getting an "Object reference not set to an instance of an object" error in Test2Password method with "possession"

Question

Here when I try to run these unit tests

using Microsoft.VisualStudio.TestTools.UnitTesting;
using OpenQA.Selenium.Appium;
using OpenQA.Selenium.Appium.Windows;
using System;
using System.Diagnostics;

namespace test
{
[TestClass]
public class AutomationTest
{
    public static WindowsDriver<WindowsElement> possession;

    [TestMethod]
    public void Test1Login()
    {
        AppiumOptions ao = new AppiumOptions();
        ao.AddAdditionalCapability("app", "Root");

        WindowsDriver<WindowsElement> windowssession =
         new WindowsDriver<WindowsElement>(new Uri("http://127.0.0.1:4723"), ao);


        AppiumOptions windowOptions = null;

        var listOfAllWindows =
         windowssession.FindElementsByXPath(@"//Window");

        Debug.WriteLine($"Elements found: {listOfAllWindows.Count}");


        foreach (var window in listOfAllWindows)

        {

            if (window.Displayed && window.Text.Contains("Aronium - POS"))
            {
                var windowHandle = window.GetAttribute("NativeWindowHandle");
                Console.WriteLine($"Window Handle: {windowHandle}");

                var handleInt = (int.Parse(windowHandle)).ToString("x");
                windowOptions = new AppiumOptions();
                windowOptions.AddAdditionalCapability("appTopLevelWindow", handleInt);
                break;
            }
        }
        WindowsDriver<WindowsElement> possession = new WindowsDriver<WindowsElement>(new Uri("http://127.0.0.1:4723"),
           windowOptions);
        possession.FindElementByAccessibilityId("passwordBox").SendKeys("Future@123");

    }

    [TestMethod]
    public void Test2Password()
    {

        possession.FindElementByClassName("Button").Click();
    }
    [ClassCleanup]
    public static void Test5Cleanup()
    {
        if (possession != null)
        {
            possession.Quit();
        }
    }
}
}

I am getting an error "Object reference not set to an instance of an object" with the 2nd method (Test2Password) Is there a way for me to declare the possession globally Or can I declare the possession as a variable I am new to C# and Winappdriver