Writing a chunk stream to a file asynchronously using hyper

I am trying to create a simple function that downloads a remote file to a local filepath using hyper. I need the file write to be asynchronous as well (in my case I am using tokio_fs for that). Here is the code:

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// Parts of the code were omitted, see the playground for full source code pub fn download_file( uri: Uri, file_location: &Path, ) -> Box<Future<Item = (), Error = DownloadFileError>> { let temp_dir_path = tempfile::tempdir().unwrap().into_path(); let file_name = match file_location.file_name() { Some(file_name) => file_name, None => return Box::new(futures::failed(DownloadFileError::IncorrectFilePath)), }; let temp_filepath = temp_dir_path.join(&file_name); let connector = HttpsConnector::new(2).unwrap(); let client: Client<_, Body> = Client::builder().build(connector); let response_future = client .get(uri) .map_err(|err| DownloadFileError::GetRequest(err)); let create_file_future = File::create(temp_filepath).map_err(|err| DownloadFileError::CreateFile(err)); Box::new( response_future .join(create_file_future) .and_then(move |(res, file)| { res.into_body() .map_err(|e| DownloadFileError::GetRequest(e)) .for_each(move |chunk| { io::write_all(file, chunk) .map(|_| ()) .map_err(|_| DownloadFileError::FileWrite) }) }), ) } 

However, I get the following error:

error[E0507]: cannot move out of captured outer variable in an `FnMut` closure --> src/lib.rs:79:39 | 75 | .and_then(move |(res, file)| { | ---- captured outer variable ... 79 | io::write_all(file, chunk) | ^^^^ cannot move out of captured outer variable in an `FnMut` closure 

Conceptually, I understand what the error means: Since a FnMut captures variables by mutable reference, I cannot move a captured variable. However, I do not understand how can I work around this problem in the example given, since I need to write the stream to the file returned by the Join future.

The write_all method from the Write trait would work here since it takes the file as a mutable reference, but the problem is that it does the writing on the same thread.