Function background_ocsp_task 

async fn background_ocsp_task(
    receiver: Receiver<CertifiedKey>,
    cache: Arc<RwLock<HashMap<Vec<u8>, Option<Arc<CertifiedKey>>>>>,
    cancel_token: CancellationToken,
    logging_tx: Vec<Sender<LogMessage>>,
) -> Result<(), Box<dyn Error + Send + Sync>>