Add example showcasing how to replace parking_lot

examples/drop_in_parking_lot.rs

@@ -0,0 +1,32 @@
+//! This example shows how you can use the [`tracing-mutex`] crate as a drop-in replacement for the
+//! parking_lot crate. By default, `tracing-mutex` offers a set of type aliases that allows you to
+//! use cycle-checking in development, and raw primitives in release mode, but this way, you can
+//! even remove the dependency altogether, or hide it behind a feature.
+//!
+//! You can use whatever conditional compilation makes sense in context.
+use std::sync::Arc;
+
+#[cfg(not(debug_assertions))]
+use parking_lot;
+
+#[cfg(debug_assertions)]
+// Note: specifically use the `tracing` module, because at this point we are very sure we want to do
+// deadlock tracing, so no need to use the automatic selection.
+use tracing_mutex::parkinglot::tracing as parking_lot;
+
+fn main() {
+    let mutex = Arc::new(parking_lot::const_mutex(0));
+
+    let handles: Vec<_> = (0..42)
+        .map(|_| {
+            let mutex = Arc::clone(&mutex);
+            std::thread::spawn(move || *mutex.lock() += 1)
+        })
+        .collect();
+
+    handles
+        .into_iter()
+        .for_each(|handle| handle.join().unwrap());
+
+    assert_eq!(*mutex.lock(), 42);
+}