Metadata returns a map (object) for a video like this: "metadata": { "0": { "video_id": 0, "filename": "", "filetype": "", "thumbnail_src": "" } and for an image it returns a slice/array like this: "metadata": [{ "image_id": , "filename": "", "filetype": "", "src": "", "fbid": 0 }] So you will have to use type assertion to handle these cases seperately.