cancel_07.cs

class Client
{
    // For classes that prohibit multiple calls to methods such as SqlConnection, add a single CancellationTokenSource to the field
    // Things like HttpClient, which may be called multiple times, are held in ObjectPool.
    
    readonly ObjectPool<CancellationTokenSource> timeoutTokenSourcePool;

    public TimeSpan Timeout { get; }

    public Client(TimeSpan timeout)
    {
        this.Timeout = timeout;
        this.timeoutTokenSourcePool = ObjectPool.Create<CancellationTokenSource>();
    }

    public async Task SendAsync()
    {
        var timeoutTokenSource = timeoutTokenSourcePool.Get();
        timeoutTokenSource.CancelAfter(Timeout);

        try
        {
            await SendCoreAsync(timeoutTokenSource.Token);
        }
        finally
        {
            // Not raised timeout, you can reuse by Reset
            if (timeoutTokenSource.TryReset())
            {
                timeoutTokenSourcePool.Return(timeoutTokenSource);
            }
        }
    }
}