You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: lib.rs
    path of file: ./repos/tower/tower-service/src
    
    the code of the file until where you have to start completion: #![warn(
    missing_debug_implementations,
    missing_docs,
    rust_2018_idioms,
    unreachable
    
///     fn call(&mut self, req: Request<Vec<u8>>) -> Self::Future {
///         // create the body
///         let body: Vec<u8> = "hello, world!\n"
///             .as_bytes()
///             .to_owned();
///         // Create the HTTP response
///         let resp = Response::builder()
///             .status(StatusCode::OK)
///             .body(body)
///             .expect("Unable to create `http::Response`");
///
///         // create a response in a future.
///         let fut = async {
///             Ok(resp)
///         };
///
///         // Return the response as an immediate future
///         Box::pin(fut)
///     }