Kestrel not shutting down gracefully

Program.cs

using System;
using System.IO;
using System.Threading;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;

namespace demo
{
    [Route("api/[controller]")]
    public class ValuesController : Controller
    {
        public static bool stopping = false;

        // GET api/values/5
        [HttpGet("{id}")]
        public string Get(int id)
        {
            while(!stopping){
                Console.WriteLine("Sleeping for 1s");
                System.Threading.Thread.Sleep(1000);
            }
                System.Threading.Thread.Sleep(1000);
            Console.WriteLine("Done sleeping");
            return "value";
        }

        // DELETE api/values/5
        [HttpDelete("{id}")]
        public void Delete(int id)
        {
            stopping = true;
             Console.WriteLine("Received shutdown request...");
            // var appLifeCycle = HttpContext.RequestServices.GetService(typeof(IApplicationLifetime)) as IApplicationLifetime;
            // appLifeCycle.StopApplication();

            Program.TokenSource.Cancel(false);
        }
    }
    
    public class Program
    {
        public static CancellationTokenSource TokenSource{get;private set;}

        public static void Main(string[] args)
        {
            var host = new WebHostBuilder()
                .UseKestrel(options => { options.ShutdownTimeout = TimeSpan.FromSeconds(5);})
                .UseContentRoot(Directory.GetCurrentDirectory())
                .UseIISIntegration()
                .UseStartup<Startup>()
                .Build();

            TokenSource = new CancellationTokenSource();
            var token = TokenSource.Token;

            host.Run(token);
            Console.WriteLine("quitting");

        }
    }
}