【Rust】axumでファイルのアップロードを受け取る

HTML側

<form action="/upload" method="post" enctype="multipart/form-data">
    <div>
        <p>name</p>
        <input type="text" name="name"><br><br>
        <input type="file" name="testfile" onchange="previewFile(this);">
    </div>
    <div>
        <input type="submit" value="送信する">
    </div>
</form>
<p>プレビュー</p>
<img id="preview">

<script>
function previewFile(file) {
    var fileData = new FileReader();
    fileData.onload = (function() {
        document.getElementById('preview').setAttribute("style","width:100px;height:100px");
        document.getElementById('preview').src = fileData.result;
        
    });
    fileData.readAsDataURL(file.files[0]);
}
</script>

axum側
axum = { version=”0.8.1″, features = [“multipart”] }
tokio = { version = “1.25”, features = [“full”] }

use tower_http::services::{ServeDir, ServeFile};
use axum::{
    extract::Multipart,
    extract::DefaultBodyLimit,
    routing::post,
    routing::get,
    Router,
};
use tokio::fs::File;
use tokio::io::AsyncWriteExt;


#[tokio::main]
async fn main() {

    let serve_dir = ServeDir::new("static").not_found_service(ServeFile::new("static"));

    let app = Router::new()
        .route("/", get(handle_index))
        .route("/upload", post(handle_upload))
        .layer(DefaultBodyLimit::max(1024 * 1024 * 1024))
        .nest_service("/static", serve_dir.clone())
        .fallback_service(serve_dir);

    let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
    axum::serve(listener, app).await.unwrap();
}

async fn handle_upload(mut multipart: Multipart)-> axum::response::Html<String> {

    while let Some(field) = multipart.next_field().await.unwrap(){
        let param_name = field.name().unwrap().to_string();
        match param_name.as_str() {
            "name" => {
                let name = field.text().await.unwrap();
                println!("tags: {}", name);
            }
            "testfile" => {
                let file_name = match field.file_name() {
                    Some(name) => name.to_owned(),
                    None => panic!("file_name is None"),
                };
                match field.bytes().await {
                    Ok(data) => {
                        println!("Length of `{}` is {} bytes", param_name, data.len());
                        let mut file = File::create(format!("./tmp/{}", file_name)).await.unwrap();
                        file.write_all(&data).await.unwrap();
                    }
                    Err(e) => {
                        eprintln!("Error reading `{}`: {}", param_name, e);
                        // return;
                    }
                }

            }
            _ => {
                println!("unknown param_name: {}", param_name);
            }
        }
    }

    let tera = tera::Tera::new("templates/*").unwrap();

    let mut context = tera::Context::new();
    context.insert("title", "Index page");

    let output = tera.render("test.html", &context);
    axum::response::Html(output.unwrap())
}

なるほど、なかなか面白い。