private async Task WriteItemsAsync(
    ChannelWriter<int> writer,
    int count,
    int delay,
    CancellationToken cancellationToken)
{
    try
    {
        for (var i = 0; i < count; i++)
        {
            // Check the cancellation token regularly so that the server will stop
            // producing items if the client disconnects.
            cancellationToken.ThrowIfCancellationRequested();
            await writer.WriteAsync(i);

            // Use the cancellationToken in other APIs that accept cancellation
            // tokens so the cancellation can flow down to them.
            await Task.Delay(delay, cancellationToken);
        }
    }
    catch (Exception ex)
    {
        writer.TryComplete(ex);
    }

    writer.TryComplete();
}