Refactor initializing tracing-subscriber

examples/low-level-rustls/src/main.rs

@@ -25,15 +25,14 @@ use tokio_rustls::{
     TlsAcceptor,
 };
 use tower::MakeService;
-use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
 
 #[tokio::main]
 async fn main() {
-    tracing_subscriber::registry()
-        .with(tracing_subscriber::EnvFilter::new(
-            std::env::var("RUST_LOG").unwrap_or_else(|_| "example_tls_rustls=debug".into()),
-        ))
-        .with(tracing_subscriber::fmt::layer())
+    tracing_subscriber::fmt()
+        .with_env_filter(
+            tracing_subscriber::EnvFilter::try_from_default_env()
+                .unwrap_or_else(|_| "example_tls_rustls=debug".into()),
+        )
         .init();
 
     let rustls_config = rustls_server_config(