Thread abort in modern .NET.

Program.cs

// See https://aka.ms/new-console-template for more information

using System.Collections;
using System.Runtime;

internal class Program
{
    public static void Main(string[] args)
    {
        var task = StartWork();
        Thread.Sleep(1000);
        MyTaskScheduler.GlobalCancellation.Cancel();
        Thread.Sleep(500);
    }

    public static Task StartWork()
    {
        return MyTask.Run(() =>
        {
            Console.WriteLine("Ticking…");
            try
            {
                while (true)
                {
                }
            }
            finally
            {
                Console.WriteLine("Finished?!");
            }
        });
    }

}

internal static class MyTask
{
    public static Task Run(Action a) =>
        Task.Factory.StartNew(
            _ => a(),
            state: null,
            cancellationToken: default,
            TaskCreationOptions.None,
            MyTaskScheduler.Instance);
}

internal class MyTaskScheduler : TaskScheduler
{
    internal static readonly MyTaskScheduler Instance = new();
    internal static readonly CancellationTokenSource GlobalCancellation = new();
    protected override void QueueTask(Task task)
    {
        Task.Run(() =>
        {
            ControlledExecution.Run(() =>
            {
                TryExecuteTask(task);
            }, GlobalCancellation.Token);
        });
    }

    protected override IEnumerable<Task>? GetScheduledTasks() => null;
    protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued) => false;
}