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: tcp_peek.rs
    path of file: ./repos/tokio/tokio/tests
    
    the code of the file until where you have to start completion: #![warn(rust_2018_idioms)]
#![cfg(all(feature = "full", not(target_os = "wasi")))] // Wasi doesn't support bind

use tokio::io::AsyncReadExt;
use tokio::net::TcpStream;

use tokio_test::assert_ok;

use std::thread;
use std::{io::Write, net};

#[tokio::test]
async fn peek() {
    let listener = net::TcpListener::bind("127.0.0.1:0").unwrap();
    let addr = listener.local_addr().unwrap();
    let t = thread::spawn(move || assert
    
async fn peek() {
    let listener = net::TcpListener::bind("127.0.0.1:0").unwrap();
    let addr = listener.local_addr().unwrap();
    let t = thread::spawn(move || assert_ok!(listener.accept()).0);

    let left = net::TcpStream::connect(addr).unwrap();
    let mut right = t.join().unwrap();
    let _ = right.write(&[1, 2, 3, 4]).unwrap();

    let mut left: TcpStream = left.try_into().unwrap();
    let mut buf = [0u8; 16];
    let n = assert_ok!(left.peek(&mut buf).await);
    assert_eq!([1, 2, 3, 4], buf[..n]);

    let n = assert_ok!(left.read(&mut buf).await);
    assert_eq!([1, 2, 3, 4], buf[..n]);
}