title: How to upload & get custom metadata with gcloud-aio-storage?
body: <p>I am using gcloud-aio-storage to cache a file. There is an option to add metadata dict in upload function</p>
  <pre><code>async def upload(self, bucket: str, object_name: str, file_data: Any,
                   *, content_type: Optional[str] = None,
                   parameters: Optional[Dict[str, str]] = None,
                   headers: Optional[Dict[str, str]] = None,
                   metadata: Optional[Dict[str, Any]])
  </code></pre>
  <p>There is also a function to download metadata
  <code>async def download_metadata(self, bucket: str, object_name: str,</code></p>
  <p>One should be able to add metadata and retrieve it later using the above functions. What am I doing wrong?</p>