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/async-std/src/io/buf_read
    
    the code of the file until where you have to start completion: mod lines;
mod read_line;
mod read_until;
mod split;

pub use lines::Lines;
pub use split::Split;

use read_line::ReadLineFuture;
use read_until::ReadUntilFutur
    
        # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
        #
        use async_std::fs::File;
        use async_std::io::BufReader;
        use async_std::prelude::*;

        let mut file = BufReader::new(File::open("a.txt").await?);

        let mut buf = Vec::with_capacity(1024);
        let n = file.read_until(b'\n', &mut buf).await?;
        #
        # Ok(()) }) }