Add a demo of the timeout method

stream-composition/src/main.rs

@@ -1,22 +1,32 @@
+use std::{pin::pin, time::Duration};
 use trpl::{ReceiverStream, Stream, StreamExt};
 
 fn main() {
     trpl::run(async {
-        let mut messages = get_messages();
+        let mut messages =
+            pin!(get_messages().timeout(Duration::from_millis(200)));
 
-        while let Some(message) = messages.next().await {
-            println!("{message}");
+        while let Some(result) = messages.next().await {
+            match result {
+                Ok(message) => println!("{message}"),
+                Err(reason) => eprintln!("Problem: {reason:?}"),
+            }
         }
-    });
+    })
 }
 
 fn get_messages() -> impl Stream<Item = String> {
     let (tx, rx) = trpl::channel();
 
-    let messages = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j"];
-    for message in messages {
-        tx.send(format!("Message: '{message}'")).unwrap();
-    }
+    trpl::spawn_task(async move {
+        let messages = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j"];
+        for (index, message) in messages.into_iter().enumerate() {
+            let time_to_sleep = if index % 2 == 0 { 100 } else { 300 };
+            trpl::sleep(Duration::from_millis(time_to_sleep)).await;
+
+            tx.send(format!("Message: '{message}'")).unwrap();
+        }
+    });
 
     ReceiverStream::new(rx)
 }