Axum fallback and hello world route

mod.rs

use axum::{
    http::{StatusCode, Uri},
    response::IntoResponse,
};
use tracing::info;

pub mod baidu;

pub async fn hello() -> &'static str {
    "Hello World!"
}

/// Fallback route handler for handling unmatched routes.
///
/// This asynchronous function takes a `Uri` as an argument, representing the unmatched route.
/// It logs a message indicating that the specified route is not found and returns a standard
/// "Not Found" response with a `StatusCode` of `404`.
///
/// # Arguments
///
/// - `uri`: The `Uri` representing the unmatched route.
///
/// # Returns
///
/// Returns a tuple `(StatusCode, &str)` where `StatusCode` is set to `NOT_FOUND` (404),
/// indicating that the route was not found, and the string "Not found" as the response body.
pub async fn fallback(uri: Uri) -> impl IntoResponse {
    info!("route {} not found", uri);
    (StatusCode::NOT_FOUND, "Not found")
}