test concurent get q from db/cache

src/main.rs

@@ -2,6 +2,7 @@
 extern crate rocket;
 
 use rocket::fs::FileServer;
+use rocket::futures::FutureExt;
 use rocket::response::Redirect;
 use rocket::State;
 use rocket_dyn_templates::tera;
@@ -86,10 +87,10 @@ async fn show_question_details(
     cache: &TemplateCache,
     id: usize,
 ) -> Template {
-    if let Some(value) = cache.get(&id) {
-        return value.render(template_name);
-    }
+    let cache_cloned = cache.clone();
 
+    let from_cache = rocket::tokio::spawn(async move { cache_cloned.get(&id) }).fuse();
+    let from_db = async move {
         match get_question(&data.db, id).await {
             Ok(question) => {
                 let mut context = tera::to_value(question).expect("question serialize");
@@ -110,6 +111,23 @@ async fn show_question_details(
                 Template::render("404", context)
             }
         }
+    }
+    .fuse();
+
+    loop {
+        rocket::tokio::select! {
+            biased;
+
+            Ok(Some(template)) = from_cache => {
+                println!("from cache");
+                break template.render(template_name)
+            },
+            template = from_db => {
+                println!("from db");
+                break template
+            }
+        }
+    }
 }
 
 #[get("/q/<id>")]