pub fn iter_batched<I, O, S, R, F>(&mut self, mut setup: S, mut routine: R, size: BatchSize)
    where
        S: FnMut() -> I,
        R: FnMut(I) -> F,
        F: Future<Output = O>,

    pub fn iter_batched_async_setup<I, O, S, R, F>(&mut self, mut setup: S, mut routine: R, size: BatchSize)
    where
        S: FnMut() -> Future<Output = I>,
        R: FnMut(I) -> F,
        F: Future<Output = O>,

   c.bench_function("async setup", |b| {
        b.to_async(Runtime::new().unwrap()).iter_batched(
            || {
                let (mut tx, rx) = std::sync::mpsc::channel();
                let s = Handle::current().spawn(async move {
                    let s = TcpStream::connect(addr).await.unwrap();
                    tx.send(s).unwrap();
                });
                rx.recv().unwrap()
            },
            |r| {
                async move {
                    println!("call {a}: {}", r.local_addr().unwrap());
                }
            },
            BatchSize::PerIteration,
        )
    });