app_async: use for_each_concurrent

app_async/src/main.rs

@@ -57,15 +57,18 @@ async fn zip_reader_task(tx: UnboundedSender<Question>) {
     let source_questions = source_questions.stream();
     pin_mut!(source_questions);
 
-    let converter = source_questions.converter().convert();
+    source_questions
-    pin_mut!(converter);
+        .converter()
-
+        .convert()
-    let mut num: u32 = 0;
+        .enumerate()
-    while let Some(mut question) = converter.next().await {
+        .map(|(num, mut question)| {
-        question.num = 1 + num;
+            question.num = 1 + (num as u32);
+            question
+        })
+        .for_each_concurrent(None, |question| async {
             tx.send(question).expect("send");
-        num += 1;
+        })
-    }
+        .await;
 
     println!("read done");
 }