Execution Context not capturing thread id

TestExecutionContext.cs

using System;
using System.Text;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Collections.Generic;

public class Test
{
    static ExecutionContext _ec;
    static int _mainThreadId;
    static ConsoleColor _mainConsoleColor;
    static object _consoleLock;

    static void Main()
    {
        _mainThreadId = Thread.CurrentThread.ManagedThreadId;
        _mainConsoleColor = Console.ForegroundColor;
        _consoleLock = new object();
        Console.WriteLine($"ThreadId: {_mainThreadId}");

        _ec = ExecutionContext.Capture();
        var tasks = new List<Task>();

        for(int i = 0; i < 20; i++)
        {
            tasks.Add(Task.Run(() =>
            {
                Console.WriteLine($"Task ThreadId: {Thread.CurrentThread.ManagedThreadId}");

                ExecutionContext.Run(_ec.CreateCopy(), delegate
                    {
                        lock (_consoleLock)
                        {
                            int id = Thread.CurrentThread.ManagedThreadId;
                            Console.ForegroundColor = id == _mainThreadId ? ConsoleColor.Green : ConsoleColor.Red;
                            Console.WriteLine($"EC ThreadId: {Thread.CurrentThread.ManagedThreadId}");
                            Console.ForegroundColor = _mainConsoleColor;
                        }
                    }, null);
            }));
        }

        Task.WaitAll(tasks.ToArray());

        Console.WriteLine("Done. Press any key to exit.");
        Console.ReadKey();
    }
}