Function run_with_streaming_response 

pub async fn run_with_streaming_response<'a, S, B, E>(
    handler: S,
) -> Result<(), Error>
where
    S: Service<Request, Response = Response<B>, Error = E>,
    S::Future: Send + 'a,
    E: Debug + Into<Diagnostic>,
    B: Body + Unpin + Send + 'static,
    B::Data: Into<Bytes> + Send,
    B::Error: Into<Error> + Send + Debug,

Runs the Lambda runtime with a handler that returns streaming HTTP responses.

See the AWS docs for response streaming.