Unity - How to get download URL after uploading image to Firebase Storage?

I am using the basic unity firebase provided by firebase to store documents.

After executing the code, I get an error message

'StorageMetadata.DownloadUrl' is deprecated: 'StorageMetadata.DownloadUrl' is deprecated. Please use StorageReference.GetDownloadUrlAsync()' instead (CS0619) [Assembly-CSharp]

After that I changed the code to

string download_url = storage_ref.Child("ss.jpg").GetDownloadUrlAsync().ToString();

in my code

images_ref.PutFileAsync(local_file).ContinueWith((Task<StorageMetadata> task) =>
{
    if(task.IsFaulted || task.IsCanceled)
    {
        Debug.Log(task.Exception.ToString());
        status.text = "Uo-oh, an error occurred!";
    }
    else
    {
        // Metadata contains file metadata such as size, content-type, and download URL.
        Firebase.Storage.StorageMetadata metadata = task.Result;
        Debug.Log("Finished uploading...");

        //string download_url = metadata.DownloadUrl.ToString(); // This shows error

        //Changed as
        string download_url = storage_ref.Child("ss.jpg").GetDownloadUrlAsync().ToString();
        Debug.Log("download url = " + download_url);
    }
});

But when using it it doesn't return the string for that URL

it returns:

下载 url = System.Threading.Tasks.Task`1[System.Uri]

After uploading, I need to get the string value of the image's downloadURL. please help.

Thank you in advance.