feat: add select3

__concurrent/async_study/examples/select3.rs

@@ -0,0 +1,40 @@
+use std::time::Duration;
+
+use tokio::{join, select};
+use tokio::sync::oneshot::channel;
+
+#[tokio::main]
+async fn main() {
+    let (tx1, rx1) = channel::<i32>();
+
+    let a = tokio::spawn(async move {
+        tokio::time::sleep(Duration::from_millis(2000)).await;
+        let _ = tx1.send(1);
+        println!(">>> send tx1");
+    });
+
+    select! {
+        a = rx1 => {
+            println!("tx: {:?}", a);
+        }
+        b = run() => {
+            println!("run: {:?}", b);
+        }
+        c = tokio::time::sleep(Duration::from_millis(1500)) => {
+            println!("timeout: {:?}", c);
+        }
+    }
+
+    println!("join: {:?}", join!(a));
+
+    println!(">> pre end");
+    tokio::time::sleep(Duration::from_millis(2000)).await;
+    println!(">> end");
+}
+
+async fn run() {
+    for i in 0.. {
+        tokio::time::sleep(Duration::from_millis(300)).await;
+        println!("# {}", i);
+    }
+}