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: etag.rs
    path of file: ./repos/loco/src/controller/middleware
    
    the code of the file until where you have to start completion: use std::task::{Context, Poll};

use axum::{body::Body, extract::Request, response::Response};
use futures_util::future::BoxFuture;
use hyper::header::{ETAG, IF_NONE_MATCH};

    
    fn call(&mut self, request: Request) -> Self::Future {
        let ifnm = request.headers().get(IF_NONE_MATCH).cloned();

        let future = self.inner.call(request);

        let res_fut = async move {
            let response = future.await.map_err(Into::into)?;
            let etag_from_response = response.headers().get(ETAG).cloned();
            if let Some(etag_in_request) = ifnm {
                if let Some(etag_from_response) = etag_from_response {
                    if etag_in_request == etag_from_response {
                        return Ok(Response::builder().status(304).body(Body::empty()).unwrap());
                    }
                }
            }
            Ok(response)
        };
        Box::pin(res_fut)
    }