Update code example for v0.2 in README

Author: davidsteiner

README.md

@@ -16,11 +16,14 @@ and Datadog.
 # Features
 
 `ddtrace` has the following features:
+
 1. tracing: utilities for building an OpenTelemetry tracer/layer that sends traces to the Datadog agent
-2. log correlation: a log formatter that converts the trace ID and span ID to the Datadog native format and injects them into the `dd.trace_id` and `dd.span_id` fields
+2. log correlation: a log formatter that converts the trace ID and span ID to the Datadog native format and injects them
+   into the `dd.trace_id` and `dd.span_id` fields
    ([more information](https://docs.datadoghq.com/tracing/other_telemetry/connect_logs_and_traces/opentelemetry/))
 3. propagation: a utility function to set the Datadog propagator as the global propagator
-4. axum (enabled via the `axum` feature): re-exposing the functionality of [axum-tracing-opentelemetry](https://github.com/davidB/axum-tracing-opentelemetry)
+4. axum (enabled via the `axum` feature): re-exposing the functionality
+   of [axum-tracing-opentelemetry](https://github.com/davidB/axum-tracing-opentelemetry)
 
 # A Complete Example
 
@@ -32,17 +35,18 @@ use std::net::SocketAddr;
 use std::time::Duration;
 
 use axum::{routing::get, Router};
-use ddtrace::axum::opentelemetry_tracing_layer;
+use ddtrace::axum::OtelAxumLayer;
+use ddtrace::error::Error;
 use ddtrace::formatter::DatadogFormatter;
 use ddtrace::set_global_propagator;
-use ddtrace::tracer::{build_layer, TraceResult};
+use ddtrace::tracer::build_layer;
 use tracing_subscriber::layer::SubscriberExt;
 use tracing_subscriber::util::SubscriberInitExt;
 
 #[tokio::main]
-async fn main() -> TraceResult<()> {
+async fn main() -> Result<(), Error> {
     let service_name = std::env::var("DD_SERVICE").unwrap_or("my-service".to_string());
-    let tracing_layer = build_layer(&service_name)?;
+    let (tracing_layer, _guard) = build_layer(service_name)?;
     tracing_subscriber::registry()
         .with(tracing_subscriber::EnvFilter::new(
             std::env::var("RUST_LOG").unwrap_or_else(|_| "info".into()),
@@ -58,16 +62,13 @@ async fn main() -> TraceResult<()> {
 
     let app = Router::new()
         .route("/", get(root))
-        .layer(opentelemetry_tracing_layer())
+        .layer(OtelAxumLayer::default())
         .route("/health", get(health));
 
     let addr = SocketAddr::from(([0, 0, 0, 0], 3025));
+    let listener = tokio::net::TcpListener::bind(addr).await.unwrap();
+    axum::serve(listener, app).await.unwrap();
     tracing::info!("listening on {}", addr);
-    axum::Server::bind(&addr)
-        .serve(app.into_make_service())
-        .with_graceful_shutdown(ddtrace::axum::shutdown_signal())
-        .await
-        .unwrap();
 
     Ok(())
 }
@@ -109,13 +110,14 @@ to set up the agent.
 # Further Context and Rationale
 
 ## Exporting Traces
+
 For traces, the official Datadog agent
 [can ingest OTel trace data](https://docs.datadoghq.com/opentelemetry/)
-with the correct environment variable settings. The traces can be sent 
+with the correct environment variable settings. The traces can be sent
 via either HTTP or gRPC. More information on this can be found
 [here](https://docs.datadoghq.com/opentelemetry/otlp_ingest_in_the_agent/?tab=docker).
 
-OpenTelemetry has an official Rust crate with extensions for major 
+OpenTelemetry has an official Rust crate with extensions for major
 formats/providers. This includes a Datadog exporter. We have found
 this exporter to be less reliable than the standard OTel exporter
 sending data to the OTel endpoint of the Datadog agent, though.
@@ -124,7 +126,8 @@ This crate builds on the OTel exporter.
 ## Propagation
 
 Two commonly used propagation standards are `B3` (OpenZipkin's propagation style)
-and Jaeger. OpenTelemetry [supports both](https://opentelemetry.io/docs/reference/specification/context/api-propagators/#propagators-distribution).
+and Jaeger.
+OpenTelemetry [supports both](https://opentelemetry.io/docs/reference/specification/context/api-propagators/#propagators-distribution).
 
 Most Datadog SDK's support both `B3` and the Datadog native propagation style.
 For example, the Python `ddtrace` library supports `B3` but it
@@ -134,8 +137,8 @@ For ease of integration with services written in other languages that use the of
 we opted for sticking with Datadog-style propagation over `B3`. This is set via the
 `set_global_propagator` function.
 
-
 # Reqwest Propagation
+
 The Python library takes care of propagation of the trace context automatically.
 Unfortunately, we need to do this manually in Rust.
 
@@ -154,7 +157,7 @@ use reqwest_tracing::TracingMiddleware;
 async fn main() {
     set_global_propagator();
     client = get_http_client();
-    
+
     // configure tracing, setup your app and inject the client
 }
 
@@ -166,4 +169,5 @@ fn get_http_client() -> ClientWithMiddleware {
 ```
 
 [crates-badge]: https://img.shields.io/crates/v/ddtrace.svg
+
 [docs-badge]: https://docs.rs/ddtrace/badge.svg