锈并发与加入和杰里*李*刘易

我试图运行两个平行功能 join.

我的代码是简单的：

tokio = { version = "1.14.0", features = ["full"] }

use tokio::join;
use std::thread::sleep;
use std::time::{Duration, Instant};

async fn fn_1() -> i8 {
  sleep(Duration::from_secs(2));

  2
}

async fn fn_2() -> i8 {
  sleep(Duration::from_secs(2));

  1
}

#[tokio::main]
async fn main() -> () {
  let now = Instant::now();

  println!("start: {:#?}", now.elapsed());

  let a = fn_1();
  let b = fn_2();

  join!(a, b);

  println!("end: {:#?}", now.elapsed());
}

但无论我做什么，这需要4s—2s + 2s—，同时它应该采取2s如果我没有记错的话:

start: 37ns
end: 4.01036111s

有什么东西是我的失踪？