Add async example

This adds a new example on how to lift events from the synchronous code
into async rust.

Cargo.toml

@@ -40,6 +40,7 @@ fsevent-sys = "4"
 winapi = { version = "0.3.8", features = ["fileapi", "handleapi", "ioapiset", "minwinbase", "synchapi", "winbase", "winnt"] }
 
 [dev-dependencies]
+futures = "0.3"
 serde_json = "1.0.39"
 tempfile = "3.2.0"
 

examples/async_monitor.rs

@@ -0,0 +1,47 @@
+use notify::{RecommendedWatcher, RecursiveMode, Event, Watcher};
+use std::path::Path;
+use futures::{SinkExt, StreamExt, channel::mpsc::{channel, Receiver}};
+
+fn async_watcher() -> notify::Result<(RecommendedWatcher, Receiver<notify::Result<Event>>)> {
+    let (mut tx, rx) = channel(1);
+
+    // Automatically select the best implementation for your platform.
+    // You can also access each implementation directly e.g. INotifyWatcher.
+    let watcher = Watcher::new_immediate(move |res| {
+        futures::executor::block_on(async {
+            tx.send(res).await.unwrap();
+        })
+    })?;
+
+    Ok((watcher, rx))
+}
+
+async fn async_watch<P: AsRef<Path>>(path: P) -> notify::Result<()> {
+    let (mut watcher, mut rx) = async_watcher()?;
+
+    // Add a path to be watched. All files and directories at that path and
+    // below will be monitored for changes.
+    watcher.watch(path, RecursiveMode::Recursive)?;
+
+    while let Some(res) = rx.next().await {
+        match res {
+            Ok(event) => println!("changed: {:?}", event),
+            Err(e) => println!("watch error: {:?}", e),
+        }
+    }
+
+    Ok(())
+}
+
+fn main() {
+    let path = std::env::args()
+        .nth(1)
+        .expect("Argument 1 needs to be a path");
+    println!("watching {}", path);
+
+    futures::executor::block_on(async {
+        if let Err(e) = async_watch(path).await {
+            println!("error: {:?}", e)
+        }
+    });
+}