make spawn layer part of built-in tcp listener util

rama/examples/tokio_tcp_echo_server.rs

@@ -1,9 +1,9 @@
 use std::time::Duration;
 
-use rama::graceful::Shutdown;
-use rama::server::tcp::TcpListener;
-use rama::service::{limit::ConcurrentPolicy, spawn::SpawnLayer};
-use rama::stream::service::EchoService;
+use rama::{
+    graceful::Shutdown, server::tcp::TcpListener, service::limit::ConcurrentPolicy,
+    stream::service::EchoService,
+};
 
 use tracing::metadata::LevelFilter;
 use tracing_subscriber::{fmt, prelude::*, EnvFilter};
@@ -25,7 +25,7 @@ async fn main() {
         TcpListener::bind("127.0.0.1:8080")
             .await
             .expect("bind TCP Listener")
-            .layer(SpawnLayer::new())
+            .spawn()
             .limit(ConcurrentPolicy::new(2))
             .timeout(Duration::from_secs(30))
             .serve_graceful::<_, EchoService, _>(guard, EchoService::new())

rama/src/server/tcp/listener.rs

@@ -95,6 +95,11 @@ impl<L> TcpListener<L> {
         self.layer(crate::service::layer_fn(f))
     }
 
+    /// Spawn a task to handle each incoming request.
+    pub fn spawn(self) -> TcpListener<Stack<crate::service::spawn::SpawnLayer, L>> {
+        self.layer(crate::service::spawn::SpawnLayer::new())
+    }
+
     /// Fail requests that take longer than `timeout`.
     pub fn timeout(
         self,