How to stop sending SSE to disconnected client?

[SuperCuber]

I have the following simple code:

#[get("/listen")]
async fn handle_listen(mut shutdown: Shutdown) -> EventStream![] {
    EventStream! {
            let mut interval = tokio::time::interval(tokio::time::Duration::from_secs(1));
            loop {
                select! {
                    _ = interval.tick() => {
                        println!("Sending ping");
                        yield Event::json(&"ping");
                    }
                    _ = &mut shutdown => {
                        break;
                    }
                }
            }
        }
}

And I have in my client a simple loop that sets up an event listener. The events arrive properly, but when I call eventSource.close() in the client the server keeps printing that the pings are being sent, despite the client no longer listening to them.

How should I detect this and stop the useless processing on the server side?