Multi-threaded Async MPSC Cache in Tokyo

main.rs

use std::collections::HashMap;
use tokio::sync::{mpsc, oneshot};

// THE BEST PART OF YOUR DAY
enum Request {
    Set(String, String), // Key and Value
    Get(String, oneshot::Sender<Option<String>>),
    Delete(String),
}

#[derive(Clone)]
struct Cache {
    req: mpsc::Sender<Request>,

}

impl Cache {
    fn new() -> Self {
        let (req, receiver) = mpsc::channel(256);
        tokio::spawn(cache_service(receiver));
        Self { req }
    }

    async fn set(&self, key: &str, value: &str) {
        self.req.send(Request::Set(
            key.to_string(),
            value.to_string(),
        )).await.ok();
    }

    async fn get(&self, key: &str) -> Option<String> {
        let (reply, receive) = oneshot::channel();
        self.req.send(Request::Get(key.to_string(), reply)).await.ok()?;
        receive.await.ok().flatten()
    }

    async fn delete(&self, key: &str) {
        self.req.send(Request::Delete(key.to_string())).await.ok();
    }
}

async fn cache_service(mut receiver: mpsc::Receiver<Request>) {
    // All data sotred here 
    let mut map: HashMap<String, String> = HashMap::new();

    while let Some(req) = receiver.recv().await {
        match req {
            Request::Set(key, value) => {
                map.insert(key, value);
            },
            Request::Get(key, reply_oneshot) => {
                reply_oneshot.send(map.get(&key).cloned()).ok();
            },
            Request::Delete(key) => {
                map.remove(&key);
            },
        }
    }
}

#[tokio::main]
async fn main() {
    println!("Hello, cache!");
    let cache = Cache::new();
    cache.set("Zergio42", "Sivan, Looons, Kyle, Bonzupii, Jefferson, zombied, mrdangwal").await;

    if let Some(value) = cache.get("Zergio42").await {
        println!("Zergio42: {value}");
    }

    cache.set("DeleteMe", "DeleteMe").await;
    if let Some(value) = cache.get("DeleteMe").await {
        println!("The DeleteMe: {value}");
    }

    cache.delete("DeleteMe").await;
    if let Some(value) = cache.get("DeleteMe").await {
        println!("NEVER WILL SEE THIS MESSSAGE: {value}");
    }
}