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: main.rs
    path of file: ./repos/gotham/examples/handlers/multipart/src
    
    the code of the file until where you have to start completion: //! An example of decoding multipart form requests
use futures_util::future::{self, FutureExt};
use gotham::handler::HandlerFuture;
use gotham::helpers::http::response::create_response;
use gotham::hyper::header::CONTENT_TYPE;
use gotham::hyper::{body, Body, HeaderMap, StatusCode};
use gotham::mime::TEXT_PLAIN;
use gotham::prelude::*;
use gotham::router::builder::build_simple_router;
use gotham::router::Router;
use gotham::state::State;
use multipart::server::Multipart;
use std::io::{Cursor, Read};
use std::pin::Pin;

/// Extracts the elements of the POST request and responds with the form keys and values
fn form_handler(mut state: State) -> Pin<Box<HandlerFuture>> {
    const BOUNDARY: 
    
    fn form_request() {
        let boundary = "--abcdef1234--";
        let body = format!(
            "--{0}\r\n\
             content-disposition: form-data; name=\"foo\"\r\n\r\n\
             bar\r\n\
             --{0}--\r\n",
            boundary
        );

        let test_server = TestServer::new(router()).unwrap();
        let client = test_server.client();
        let mut request = client.post("http://localhost", body, MULTIPART_FORM_DATA);

        let content_type_string = format!("multipart/form-data; boundary={}", boundary);
        request.headers_mut().insert(
            CONTENT_TYPE,
            HeaderValue::from_str(content_type_string.as_str()).unwrap(),
        );
        let response = request.perform().unwrap();
        assert_eq!(response.status(), StatusCode::OK);
        let body = response.read_body().unwrap();
        let r = String::from_utf8(body).unwrap();
        assert_eq!(r, "bar");
    }