Fix issue 4

[cuteant]

Fix #4

[yyjdelete]

@cuteant
By the way, can you check the implement for LoopExecutor.TaskDelay(int) is right? First notice this in #37 (comment).

SpanNetty/src/DotNetty.Transport.Libuv/LoopExecutor.cs

Lines 181 to 184 in ada8a3a

	protected override void TaskDelay(int millisecondsTimeout)
	{
	_ = _timerHandle.Start(millisecondsTimeout, 0);
	}

It's only used here, and I think it required to be sync blocked here like the base class does , but the override in LoopExecutor don't look like an sync wait(Not sure whether it will actual affact anything or not)

SpanNetty/src/DotNetty.Common/Concurrency/SingleThreadEventExecutor.cs

Lines 902 to 954 in 7fcaab4

	[MethodImpl(MethodImplOptions.NoInlining)]
	private bool ConfirmShutdownSlow()
	{
	if (!InEventLoop) { ThrowHelper.ThrowInvalidOperationException_Must_be_invoked_from_an_event_loop(); }
	CancelScheduledTasks();
	if (0ul >= (ulong)_gracefulShutdownStartTime)
	{
	_gracefulShutdownStartTime = GetTimeFromStart();
	}
	if (RunAllTasks() || RunShutdownHooks())
	{
	if (IsShutdown)
	{
	// Executor shut down - no new tasks anymore.
	return true;
	}
	// There were tasks in the queue. Wait a little bit more until no tasks are queued for the quiet period or
	// terminate if the quiet period is 0.
	// See https://github.com/netty/netty/issues/4241
	if (0ul >= (ulong)Volatile.Read(ref v_gracefulShutdownQuietPeriod))
	{
	return true;
	}
	_taskQueue.TryEnqueue(WakeupTask);
	return false;
	}
	long nanoTime = GetTimeFromStart();
	if (IsShutdown || (nanoTime - _gracefulShutdownStartTime > Volatile.Read(ref v_gracefulShutdownTimeout)))
	{
	return true;
	}
	if (nanoTime - _lastExecutionTime <= Volatile.Read(ref v_gracefulShutdownQuietPeriod))
	{
	// Check if any tasks were added to the queue every 100ms.
	// TODO: Change the behavior of takeTask() so that it returns on timeout.
	_taskQueue.TryEnqueue(WakeupTask);
	TaskDelay(100);
	return false;
	}
	// No tasks were added for last quiet period - hopefully safe to shut down.
	// (Hopefully because we really cannot make a guarantee that there will be no execute() calls by a user.)
	return true;
	}

SpanNetty/src/DotNetty.Common/Concurrency/SingleThreadEventExecutor.cs

Lines 319 to 322 in 7fcaab4

	protected virtual void TaskDelay(int millisecondsTimeout)
	{
	Thread.Sleep(millisecondsTimeout);
	}

[cuteant]

@yyjdelete 我想了下，真是有问题，LoopExecutor中实现的 TaskDelay 的调用分两种情况

1. 在 Run 方法中执行，这儿逻辑没问题

   SpanNetty/src/DotNetty.Transport.Libuv/LoopExecutor.cs

   Line 285 in 7fcaab4

   protected override void Run()

2. 在 CleanupAndTerminate 方法中执行，这儿就出问题了，因为这时候 loop已经关闭了
   

   SpanNetty/src/DotNetty.Transport.Libuv/LoopExecutor.cs

   Line 157 in 7fcaab4

   CleanupAndTerminate(false);

[cuteant]

上面表述不准确，实际上 LoopExecutor调用CleanupAndTerminate不应对任务进行处理，要稍微修改下DoShutdown这个方法