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: mod.rs
    path of file: ./repos/ureq/src/test
    
    the code of the file until where you have to start completion: use crate::error::Error;
use crate::pool::PoolReturner;
use crate::stream::{remote_addr_for_test, ReadOnlyStream, Stream};
use crate::unit::Unit;
use crate::ReadWrite;
use once_cell::sync::Lazy;
use std::collections::HashMap;
use std::fmt;
use std::io::{self, Cursor, Read, Write};
use std::net::TcpStream;
use std::sync::{Arc, Mutex};

mod agent_test;
mod body_read;
mod body_send;
mod query_string;
mod range;
mod redirect;
mod simple;
mod timeout;

type RequestHandler = dyn Fn(&Unit) -> Result<Stream, Error> + Send + 'static;

#[allow(clippy::type_complexity)]
pub(crate) static 
    
pub(crate) fn resolve_handler(unit: &Unit) -> Result<Stream, Error> {
    let path = unit.url.path();
    // The only way this can panic is if
    // 1. `remove(path).unwrap()` panics, in which case the HANDLERS haven't been modified.
    // 2. `make_hash` for `handlers.insert` panics (in `set_handler`), in which case the HANDLERS haven't been modified.
    // In all cases, another test will fail as a result, so it's ok to continue other tests in parallel.
    let mut handlers = match TEST_HANDLERS.lock() {
        Ok(h) => h,
        Err(poison) => poison.into_inner(),
    };
    let handler = handlers.remove(path)
        .unwrap_or_else(|| panic!("call make_response(\"{}\") before fetching it in tests (or if you did make it, avoid fetching it more than once)", path));
    drop(handlers);
    handler(unit)
}