ISerialClosingPluginOnSerialClosing 方法
            即将断开连接(仅主动断开时有效)。
            
命名空间: TouchSocket.SerialPorts程序集: TouchSocket.SerialPorts (在 TouchSocket.SerialPorts.dll 中) 版本:4.0.0-beta.143+5fcca7a4e70968794985dc3793adc50531308be6
Task OnSerialClosing(
	ISerialPortSession client,
	ClosingEventArgs e
)
Function OnSerialClosing ( 
	client As ISerialPortSession,
	e As ClosingEventArgs
) As Task
abstract OnSerialClosing : 
        client : ISerialPortSession * 
        e : ClosingEventArgs -> Task 
- client  ISerialPortSession
 - 串口会话客户端
 - e  ClosingEventArgs
 - 关闭事件参数
 
Task异步任务