Using the exit command after installing the Oracle plugin causes the cli to become unresponsive

[ProDog]

Describe the bug
Using the exit command after installing the OracleService plugin causes the neo-cli to become unresponsive.

To Reproduce
Steps to reproduce the behavior:

1. install OracleService plugin;
2. start neo-cli;
3. execute the exit command.

Expected behavior
Exit cli correctly.

Screenshots

Platform:

• OS: [All]
• Version [The latest master]

[shargon]

It's work for me, do you have anything else?

[ProDog]

No, I just add OracleService plugin and it will appear. Removing the OracleService plugin and it will work.

[ProDog]

Here into the loop and caused the bug.

neo-modules/src/OracleService/OracleService.cs

Lines 63 to 70 in 3f99dad

	public override void Dispose()
	{
	OnStop();
	while (!stopped)
	Thread.Sleep(100);
	foreach (var p in protocols)
	p.Value.Dispose();
	}

neo-modules/src/OracleService/OracleService.cs

Lines 99 to 107 in 3f99dad

	private void OnStop()
	{
	cancelSource.Cancel();
	if (timer != null)
	{
	timer.Dispose();
	timer = null;
	}
	}

[erikzhang]

neo-modules/src/OracleService/OracleService.cs

Lines 171 to 192 in 3f99dad

	private static async Task SendContentAsync(string url, string content)
	{
	try
	{
	HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
	request.Method = "POST";
	request.ContentType = "application/json";
	request.Timeout = 5000;
	using (StreamWriter dataStream = new StreamWriter(await request.GetRequestStreamAsync()))
	{
	await dataStream.WriteAsync(content);
	}
	HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync();
	if (response.ContentLength > ushort.MaxValue) throw new Exception("The response it's bigger than allowed");
	StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
	await reader.ReadToEndAsync();
	}
	catch (Exception e)
	{
	Log($"Failed to send the response signature to {url}, as {e.Message}", LogLevel.Warning);
	}
	}

This method needs to use CancellationToken.

[chenzhitong]

Is this okay?

private void OnStop()
{
    cancelSource.Cancel();
    stopped = true; // add this line
    if (timer != null)
    {
        timer.Dispose();
        timer = null;
    }
}

[shargon]

@chenzhitong At the end of the method it should be ok