未写入字节超过给定时间段，如何取消流CopyToAsync

using System;
using System.IO;
using System.Threading;
using System.Threading.Tasks;

public class Program
{
    public static async Task Main()
    {
        // 创建源流和目标流
        using var sourceStream = new MemoryStream();
        using var targetStream = new MemoryStream();

        // 将源流填充一些数据
        byte[] data = new byte[1024];
        new Random().NextBytes(data);
        await sourceStream.WriteAsync(data, 0, data.Length);

        // 创建 CancellationTokenSource 对象
        using var cancellationTokenSource = new CancellationTokenSource();

        // 注册取消回调函数
        cancellationTokenSource.Token.Register(() =>
        {
            Console.WriteLine("复制操作已取消");
            // 执行其他取消操作的逻辑
        });

        try
        {
            // 执行异步复制操作
            await CopyStreamAsync(sourceStream, targetStream, cancellationTokenSource.Token);
            Console.WriteLine("复制操作已完成");
        }
        catch (OperationCanceledException)
        {
            Console.WriteLine("复制操作已取消");
        }
    }

    public static async Task CopyStreamAsync(Stream source, Stream target, CancellationToken cancellationToken)
    {
        byte[] buffer = new byte[1024];
        int bytesRead;

        while ((bytesRead = await source.ReadAsync(buffer, 0, buffer.Length, cancellationToken)) > 0)
        {
            cancellationToken.ThrowIfCancellationRequested();
            await target.WriteAsync(buffer, 0, bytesRead, cancellationToken);
        }
    }
}