When your Timer is GC.Collected its action will never fire

TestTimerGC.cs

using System;
using System.Collections.Concurrent;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

// This piece of code shows that if you do not assign a variable to your Timer (like in Runner.ExecuteWithTimeout_NotWorking)
// your timer may be Garbage Collected before its action fires.
// In case of the code below this will result in the Tasks running for ever.
// Calling GC.Collect() forces Garbage Collection to fake a real aplicaiton and long running Tasks.
// use: var tasks = Enumerable.Range(1, 10).Select(x => new Runner().ExecuteWithTimeout_NotWorking()).ToArray();
//     to create 10 Tasks which never end
// use: var tasks = Enumerable.Range(1, 10).Select(x => new Runner().ExecuteWithTimeout()).ToArray();
//     to see how it should be working correctly

class Program
{
    public static ConcurrentBag<int> bag = new ConcurrentBag<int>();

    static void Main(string[] args)
    {
        Task.Run(async () =>
        {
//            var tasks = Enumerable.Range(1, 10).Select(x => new Runner().ExecuteWithTimeout()).ToArray(); // this is how it should be done
            var tasks = Enumerable.Range(1, 10).Select(x => new Runner().ExecuteWithTimeout_NotWorking()).ToArray(); // this will be running for ever
            while (true)
            {
                GC.Collect();
                Thread.Sleep(500);
                Console.WriteLine("currently there are: " + bag.Count + " tasks running");
            }
        }).GetAwaiter().GetResult();
    }
}

public class Runner
{
    public async Task ExecuteWithTimeout()
    {
        Program.bag.Add(1);
        bool kill = false;
        var timer = new Timer(_ => { 
                Console.WriteLine("timer action!");
                kill = true;
            }, null, 5 * 1000, int.MaxValue);

        Console.WriteLine("waiting for exit of task");
        while (!kill)
        {
            await Task.Delay(500);
        }

        Console.WriteLine("ended Task");
        Program.bag.TryTake(out int x);
        timer.Dispose();
    }

    public async Task ExecuteWithTimeout_NotWorking()
    {
        Program.bag.Add(1);
        bool kill = false;
        new Timer(_ => {
                Console.WriteLine("timer action!");
                kill = true;
            }, null, 5 * 1000, int.MaxValue);

        Console.WriteLine("waiting for exit of task");
        while (!kill)
        {
            await Task.Delay(500);
        }

        Console.WriteLine("ended Task");
        Program.bag.TryTake(out int x);
    }
}