fix for #762

Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClient.cs

@@ -349,7 +349,7 @@ namespace MQTTnet.Extensions.ManagedClient
                     // of the messages, the DropOldestQueuedMessage strategy would
                     // be unable to know which message is actually the oldest and would
                     // instead drop the first item in the queue.
-                    var message = _messageQueue.PeekAndWait();
+                    var message = _messageQueue.PeekAndWait(cancellationToken);
                     if (message == null)
                     {
                         continue;

Source/MQTTnet/Internal/BlockingQueue.cs

@@ -8,7 +8,7 @@ namespace MQTTnet.Internal
     {
         private readonly object _syncRoot = new object();
         private readonly LinkedList<TItem> _items = new LinkedList<TItem>();
-        private readonly ManualResetEvent _gate = new ManualResetEvent(false);
+        private readonly ManualResetEventSlim _gate = new ManualResetEventSlim(false);
 
         public int Count
         {
@@ -32,7 +32,7 @@ namespace MQTTnet.Internal
             }
         }
 
-        public TItem Dequeue()
+        public TItem Dequeue(CancellationToken cancellationToken = default)
         {
             while (true)
             {
@@ -52,11 +52,11 @@ namespace MQTTnet.Internal
                     }
                 }
 
-                _gate.WaitOne();
+                _gate.Wait(cancellationToken);
             }
         }
         
-        public TItem PeekAndWait()
+        public TItem PeekAndWait(CancellationToken cancellationToken = default)
         {
             while (true)
             {
@@ -73,7 +73,7 @@ namespace MQTTnet.Internal
                     }
                 }
 
-                _gate.WaitOne();
+                _gate.Wait(cancellationToken);
             }
         }