feat: add select

__concurrent/async_study/examples/select.rs

@@ -0,0 +1,24 @@
+use std::time::Duration;
+use tokio::sync::oneshot::channel;
+
+#[tokio::main]
+async fn main() {
+    let (tx1, rx1) = channel::<i32>();
+    let (_tx2, rx2) = channel::<i32>();
+
+    tokio::spawn(async move {
+        tokio::time::sleep(Duration::from_millis(200)).await;
+        tx1.send(1);
+    });
+
+    println!("start select");
+    tokio::select! {
+        val = rx1 => {
+            println!("rx1 completed first with {:?}", val);
+        }
+        val = rx2 => {
+            println!("rx2 completed first with {:?}", val);
+        }
+    }
+    println!("end select");
+}