You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: main.rs
    path of file: ./repos/rules_rust/examples/crate_universe_unnamed/vendor_remote_pkgs/src
    
    the code of the file until where you have to start completion: //! Copied from https://github.com/tokio-rs/axum/blob/v0.2.5/examples/testing/src/main.rs

use axum::{
    routing::{get, post},
    Json, Router,
};
use tower_http::trace::TraceLayer;

#[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() 
    
    async fn hello_world() {
        let app = app();

        // `Router` implements `tower::Service<Request<Body>>` so we can
        // call it like any tower service, no need to run an HTTP server.
        let response = app
            .oneshot(Request::builder().uri("/").body(Body::empty()).unwrap())
            .await
            .unwrap();

        assert_eq!(response.status(), StatusCode::OK);

        let body = hyper::body::to_bytes(response.into_body()).await.unwrap();
        assert_eq!(&body[..], b"Hello, World!");
    }