AsyncProgram.cs

using System;
using System.Threading;

static class AsyncProgram
{
	private static readonly CancellationTokenSource cts = new CancellationTokenSource();
	public static CancellationToken CancellationToken => cts.Token;

	static AsyncProgram()
	{
		Console.CancelKeyPress += EventHandler;
		AppDomain.CurrentDomain.ProcessExit += EventHandler;

		static void EventHandler(Object? sender, EventArgs e)
		{
			if (cts.IsCancellationRequested)
				return;
			cts.Cancel();
		}
	}
}