impl<T> PeekableReceiver<T> {
    pub fn new(receiver: Receiver<T>) -> Self {
        Self {
            inner: Arc::new(Mutex::new(receiver)),
            next_item: None,
        }
    }

    pub async fn peek(&mut self) -> Option<&T> {
        if self.next_item.is_none() {
            let mut receiver = self.inner.lock().await;
            self.next_item = receiver.recv().await;
        }
        self.next_item.as_ref()
    }

   pub fn advance(&mut self) {
       self.next_item = None;
   }

    pub async fn recv(&mut self) -> Option<T> {
        if self.next_item.is_none() {
            let mut receiver = self.inner.lock().await;
            receiver.recv().await
        } else {
            self.next_item.take()
        }
    }
}