Drain joinset before completing migration

src/migrate_store.rs

@@ -126,6 +126,10 @@ where
         joinset.spawn_local(async move { migrate_hash(&state, hash).await });
     }
 
+    while let Some(res) = joinset.join_next().await {
+        res.map_err(|_| UploadError::Canceled)??;
+    }
+
     // clean up the migration table to avoid interfering with future migrations
     repo.clear().await?;