Add example for graceful shutdown

rumqttd/examples/graceful_shutdown.rs

@@ -0,0 +1,43 @@
+use rumqttd::{Broker, Config};
+use tracing::Level;
+
+use core::time::Duration;
+use std::thread;
+
+fn main() {
+    let builder = tracing_subscriber::fmt()
+        .pretty()
+        .with_max_level(Level::DEBUG)
+        .with_line_number(false)
+        .with_file(false)
+        .with_thread_ids(false)
+        .with_thread_names(false);
+
+    builder
+        .try_init()
+        .expect("initialized subscriber succesfully");
+
+    // As examples are compiled as seperate binary so this config is current path dependent. Run it
+    // from root of this crate
+    let config = config::Config::builder()
+        .add_source(config::File::with_name("rumqttd.toml"))
+        .build()
+        .unwrap();
+
+    let config: Config = config.try_deserialize().unwrap();
+
+    dbg!(&config);
+
+    let mut broker = Broker::new(config);
+
+    let handler = broker.shutdown_handler();
+
+    thread::spawn(move || {
+        broker.start().unwrap();
+        println!("Shutdown handler called");
+    });
+
+    thread::sleep(Duration::from_secs(1));
+    handler.shutdown_broker();
+    thread::sleep(Duration::from_secs(1));
+}