extern crate tokio;

use tokio::prelude::*;

fn files() -> impl Stream<Item = u32, Error = std::io::Error> {
    stream::iter_ok(vec![10, 20, 30])
}

fn read_chunks(file: u32) -> impl Stream<Item = u32, Error = std::io::Error> {
    stream::iter_ok(vec![file + 1, file + 2, file + 3, file + 4, file + 5])
}
fn main() {
    let run = files()
        .map(move |fh| {
            println!("Streaming file {}", fh);
            read_chunks(fh)
                .map(move |ret| {
                    println!("{}", ret);
                })
                .for_each(|_| Ok(()))
        })
        .buffer_unordered(2)
        .collect()
        .map(|_| ())
        .map_err(|_| ());

    tokio::run(run);
}