Simple hyper server with limited number of concurret requests

Cargo.toml

[package]
name = "tower-test"
version = "0.1.0"
edition = "2021"

[dependencies]
color-eyre = "0.6.1"
hyper = { version = "0.14.18", features = ["full"] }
tokio = { version = "1.17.0", features = ["full"] }
tower = { version = "0.4.12", features = ["full"] }

main.rs

use std::{convert::Infallible, net::Ipv4Addr, sync::Arc};

use color_eyre::eyre;
use hyper::{Body, Response};
use tokio::sync::Semaphore;
use tower::{limit::ConcurrencyLimit, make::Shared, ServiceBuilder};

#[tokio::main]
async fn main() -> eyre::Result<()> {
    let semaphore = Arc::new(Semaphore::const_new(2));
    let service = ServiceBuilder::new()
        .layer_fn(|inner| ConcurrencyLimit::with_semaphore(inner, semaphore.clone()))
        .service_fn(
            |_req| async move { Ok::<_, Infallible>(Response::new(Body::from("Hello World"))) },
        );
    let make_service = Shared::new(service);
    let server =
        hyper::Server::bind(&(Ipv4Addr::LOCALHOST, 8080).try_into().unwrap()).serve(make_service);

    Ok(server.await?)
}