Criando uma API Streaming com .NET Core

ClienteController.cs

[HttpGet]
[Route("Streaming")]
public IActionResult Stream()
{
    return new PushStreamResult(OnStreamAvailable, "text/event-stream", HttpContext.RequestAborted);
}

private void OnStreamAvailable(Stream stream, CancellationToken requestAborted)
{
    var wait = requestAborted.WaitHandle;
    var client = new StreamWriter(stream);
    _clients.Add(client);

    wait.WaitOne();

    StreamWriter ignore;
    _clients.TryTake(out ignore);
}