Enqueue tasks on unity main thread

ThreadController.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using System;
using System.Threading.Tasks;

public class ThreadController : MonoBehaviour
{
  private static ThreadController _instance = null;
  private static readonly Queue<Action> _executionQueue = new Queue<Action>();

  public static ThreadController Instance()
  {
    if (!Exists())
    {
      throw new Exception("ThreadController needs to be added to your scene.");
    }
    return _instance;
  }
  void Awake()
  {
    if (_instance == null)
    {
      _instance = this;
      DontDestroyOnLoad(this.gameObject);
    }
  }

  public void Update()
  {
    lock (_executionQueue)
    {
      while (_executionQueue.Count > 0)
      {
        _executionQueue.Dequeue().Invoke();
      }
    }
  }

  public void Enqueue(IEnumerator action)
  {
    lock (_executionQueue)
    {
      _executionQueue.Enqueue(() => {
        StartCoroutine(action);
      });
    }
  }

  public void Enqueue(Action action)
  {
    Enqueue(ActionWrapper(action));
  }
  
  public Task EnqueueAsync(Action action)
  {
    var tcs = new TaskCompletionSource<bool>();

    void WrappedAction()
    {
      try
      {
        action();
        tcs.TrySetResult(true);
      }
      catch (Exception ex)
      {
        tcs.TrySetException(ex);
      }
    }

    Enqueue(ActionWrapper(WrappedAction));
    return tcs.Task;
  }

  IEnumerator ActionWrapper(Action callback)
  {
    callback();
    yield return null;
  }

  public static bool Exists()
  {
    return _instance != null;
  }

  void OnDestroy()
  {
    _instance = null;
  }
}