MonoBehaviourSynchronizationContext.cs

public class MonoBehaviourSynchronizationContext : SynchronizationContext
{
    object gate = new object();
    Queue<KeyValuePair<SendOrPostCallback, object>> actionQueue = new Queue<KeyValuePair<SendOrPostCallback, object>>();

    public MonoBehaviourSynchronizationContext(MonoBehaviour monoBehaviour)
    {
        monoBehaviour.StartCoroutine(Run());
    }

    IEnumerator Run()
    {
        while (true)
        {
            lock (gate)
            {
                while (actionQueue.Count != 0)
                {
                    var action = actionQueue.Dequeue();
                    try
                    {
                        action.Key(action.Value);
                    }
                    catch (Exception ex)
                    {
                        Debug.LogException(ex);
                    }
                }
            }
            yield return null;
        }
    }

    public override void Send(SendOrPostCallback d, object state)
    {
        lock (gate)
        {
            actionQueue.Enqueue(new KeyValuePair<SendOrPostCallback, object>(d, state));
        }
    }

    public override void Post(SendOrPostCallback d, object state)
    {
        lock (gate)
        {
            actionQueue.Enqueue(new KeyValuePair<SendOrPostCallback, object>(d, state));
        }
    }
}