We need to actually flush the async File to ensure everything gets wr…

…itten.

The `Drop` impl won't do it for us

src/http_assets.rs

@@ -76,7 +76,9 @@ impl AssetReader for HttpAssetReader {
                 // Write asset to cache, but ensure only one HttpAssetReader writes at any given point in time
                 if self.sync.write().unwrap().insert(cache_path.clone()) {
                     async_fs::create_dir_all(cache_path.parent().unwrap()).await?;
-                    File::create(&cache_path).await?.write_all(&bytes).await?;
+                    let mut file = File::create(&cache_path).await?;
+                    file.write_all(&bytes).await?;
+                    file.flush().await?;
                 }
             }
             Ok(Box::new(VecReader::new(bytes)) as Box<Reader<'static>>)