async read file using join!

use tokio::io::AsyncReadExt;

#[tokio::main]
async fn main() {
    println!("Start");
    let future = run();

    println!("Before await");
    future.await;

    println!("End");
}

async fn run() {
    // sequentially
    do_something().await;
    read_file().await;

    // concurrently
    // tokio::join!(
    //     do_something(),
    //     read_file(),
    // );
}

async fn do_something() {
    println!("Start to do something");
    tokio::time::sleep(tokio::time::Duration::from_secs(1)).await;
    println!("End   to do something");
}

async fn read_file() {
    println!("Start reading");
    let mut fh = tokio::fs::File::open("src/main.rs").await.unwrap();
    let mut content = vec![];
    fh.read_to_end(&mut content).await.unwrap();
    println!("End   reading {} bytes", content.len());
}

Sequentially

Start
Before await
Start to do something
End   to do something
Start reading
End   reading 780 bytes
End

concurrently with join!

Start
Before await
Start to do something
End   to do something
Start reading
End   reading 780 bytes
End

Cargo.toml

[package]
name = "demo"
version = "0.1.0"
edition = "2024"

[dependencies]
tokio = { version = "1.39.2", features = ["full"] }