Source Code added

mobile/lib/utils/async_mutex.dart

@@ -0,0 +1,21 @@
+import 'dart:async';
+
+/// Async mutex to guarantee actions are performed sequentially and do not interleave
+class AsyncMutex {
+  Future _running = Future.value(null);
+  int _enqueued = 0;
+
+  int get enqueued => _enqueued;
+
+  /// Execute [operation] exclusively, after any currently running operations.
+  /// Returns a [Future] with the result of the [operation].
+  Future<T> run<T>(Future<T> Function() operation) {
+    final completer = Completer<T>();
+    _enqueued++;
+    _running.whenComplete(() {
+      _enqueued--;
+      completer.complete(Future<T>.sync(operation));
+    });
+    return _running = completer.future;
+  }
+}