Multiclient bug fixed

mROA/Implementation/CancellationRepository.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Threading;
 using mROA.Abstract;
@@ -7,7 +8,7 @@ namespace mROA.Implementation
 {
     public class CancellationRepository : ICancellationRepository
     {
-        private Dictionary<Guid, CancellationTokenSource> _cancellations = new();
+        private ConcurrentDictionary<Guid, CancellationTokenSource> _cancellations = new();
 
         public void RegisterCancellation(Guid id, CancellationTokenSource cts)
         {
@@ -16,12 +17,12 @@ namespace mROA.Implementation
 
         public CancellationTokenSource? GetCancellation(Guid id)
         {
-            return _cancellations.GetValueOrDefault(id, null);
+            return _cancellations.GetValueOrDefault(id);
         }
 
         public void FreeCancelation(Guid id)
         {
-            _cancellations.Remove(id);
+            _cancellations.Remove(id, out _);
         }
 
         public void Inject<T>(T dependency)