fix: as_yielded

a_sync/utils/iterators.py

@@ -18,6 +18,8 @@ async def exhaust_iterator(iterator: AsyncIterator[T], *, queue: Optional[asynci
 
 async def exhaust_iterators(iterators, *, queue: Optional[asyncio.Queue] = None) -> None:
     await asyncio.gather(*[exhaust_iterator(iterator, queue=queue) for iterator in iterators]) 
+    if queue:
+        queue.put_nowait(_Done())
 
 T0 = TypeVar('T0')
 T1 = TypeVar('T1')
@@ -58,16 +60,20 @@ async def as_yielded(*iterators: AsyncIterator[T]) -> AsyncIterator[T]:
     def done_callback(t: asyncio.Task) -> None:
         if t.exception() and not next_fut.done(): 
             next_fut.set_exception(t.exception())
+
     task.add_done_callback(done_callback)
     while not task.done():
         next_fut = asyncio.get_event_loop().create_future()
         get_task = asyncio.create_task(coro=queue.get(), name=str(queue))
         _chain_future(get_task, next_fut)
-        yield await next_fut
-        for next in queue.get_nowait(-1):
-            yield next
-
+        for item in (await next_fut, *queue.get_nowait(-1)):
+            if isinstance(item, _Done):
+                return
+            yield item
+
     if e := task.exception():
         get_task.cancel()
         raise e
 
+class _Done:
+    pass