Replace set_var usage in examples (#829)

* examples: Fix inconsistent toml formatting

* examples: Replace set_var usage

examples/error-handling-and-dependency-injection/src/main.rs

@@ -18,18 +18,18 @@ use axum::{
 use serde::{Deserialize, Serialize};
 use serde_json::json;
 use std::{net::SocketAddr, sync::Arc};
+use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
 use uuid::Uuid;
 
 #[tokio::main]
 async fn main() {
-    // Set the RUST_LOG, if it hasn't been explicitly defined
-    if std::env::var_os("RUST_LOG").is_none() {
-        std::env::set_var(
-            "RUST_LOG",
-            "example_error_handling_and_dependency_injection=debug",
-        )
-    }
-    tracing_subscriber::fmt::init();
+    tracing_subscriber::registry()
+        .with(tracing_subscriber::EnvFilter::new(
+            std::env::var("RUST_LOG")
+                .unwrap_or_else(|_| "example_error_handling_and_dependency_injection=debug".into()),
+        ))
+        .with(tracing_subscriber::fmt::layer())
+        .init();
 
     // Inject a `UserRepo` into our handlers via a trait object. This could be
     // the live implementation or just a mock for testing.