Function cancel_background_query 

async fn cancel_background_query(
    cancel_token: &CancelToken,
    url: &str,
    timeout: Duration,
)

Best-effort cancellation of the in-progress query on the connection cancel_token was derived from. Opens a fresh connection to send the cancel request. Cancellation is inherently racy and the caller aborts the task regardless, so failures are logged rather than propagated.