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: mod.rs
    path of file: ./repos/rustus/src/server
    
    the code of the file until where you have to start completion: use std::{
    net::{Ipv4Addr, SocketAddr, SocketAddrV4},
    sync::Arc,
    time::Duration,
};

use crate::{
    config::Config, errors::RustusResult, state::RustusState, utils::headers::HeaderMapExt,
};
use axum::{
    extract::{ConnectInfo, DefaultBodyLimit, Request, State},
    http::{HeaderValue, StatusCode},
    response::{IntoResponse, Response},
    Router, ServiceExt,
};
use tower::Layer;
use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};

mod cors;
mod routes;

async fn method_replacer(
    mut req: axum::extract::Request,
    next: axum::middleware::Next,
) -> impl axum::response::IntoResponse {
    if let Some(new_method) = req.headers().get_method_override() {
        *req.method_mut() = new_method;
        req.headers_mut()
    
pub async fn start(config: Config) -> RustusResult<()> {
    let behind_proxy = config.behind_proxy;
    let default_addr = ConnectInfo(SocketAddr::V4(SocketAddrV4::new(
        Ipv4Addr::new(0, 0, 0, 0),
        0,
    )));

    let mut sentry_layer = None;
    if config.sentry_config.dsn.is_some() {
        sentry_layer = Some(sentry_tracing::layer());
    }

    tracing_subscriber::registry()
        .with(tracing_subscriber::filter::LevelFilter::from_level(
            config.log_level,
        ))
        .with(
            tracing_subscriber::fmt::layer()
                .with_level(true)
                .with_file(false)
                .with_line_number(false)
                .with_target(false),
        )
        .with(sentry_layer)
        .init();

    let tracer = tower_http::trace::TraceLayer::new_for_http()
        .make_span_with(move |request: &Request| {
            let path = request.uri().path().to_string();
            let socket_addr = request
                .extensions()
                .get::<ConnectInfo<SocketAddr>>()
                .unwrap_or(&default_addr);
            let ip = request.headers().get_remote_ip(socket_addr, behind_proxy);
            tracing::info_span!(
                "request",
                method = ?request.method(),
                path,
                version = ?request.version(),
                ip = ip,
                status = tracing::field::Empty,
            )
        })
        .on_response(
            move |response: &Response, latency: Duration, span: &tracing::Span| {
                span.record("status", response.status().as_u16());
                span.record("duration", latency.as_millis());
                if config.no_access {
                    return;
                }
                if response.headers().contains_key("X-NO-LOG") {
                    return;
                }
                tracing::info!("access log");
            },
        );

    let state = Arc::new(RustusState::from_config(&config).await?);
    let tus_app = get_router(state);
    let mut main_router = axum::Router::new()
        .route("/health", axum::routing::get(healthcheck))
        .nest(&config.url, tus_app)
        .fallback(fallback)
        .layer(tracer);

    if config.sentry_config.dsn.is_some() {
        main_router = main_router
            .layer(sentry_tower::NewSentryLayer::new_from_top())
            .layer(sentry_tower::SentryHttpLayer::new());
    }

    let listener = tokio::net::TcpListener::bind((config.host.clone(), config.port)).await?;
    tracing::info!("Starting server at http://{}:{}", config.host, config.port);
    axum::serve(
        listener,
        axum::middleware::from_fn(method_replacer)
            .layer(main_router)
            .into_make_service_with_connect_info::<SocketAddr>(),
    )
    .await?;
    Ok(())
}