Fix issue with concurrent logging (#63)

* Fix issue with concurrent logging

* Fix namespace + code format/cleanup

test/WireMock.Net.Tests/ObservableLogEntriesTest.cs

@@ -1,5 +1,10 @@
 using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net;
 using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
 using NFluent;
 using WireMock.RequestBuilders;
 using WireMock.ResponseBuilders;
@@ -8,7 +13,7 @@ using Xunit;
 
 namespace WireMock.Net.Tests
 {
-    public class ObservableLogEntriesTest: IDisposable
+    public class ObservableLogEntriesTest : IDisposable
     {
         private FluentMockServer _server;
 
@@ -35,6 +40,42 @@ namespace WireMock.Net.Tests
             Check.That(count).Equals(1);
         }
 
+        [Fact]
+        public async Task ParallelTest()
+        {
+            var expectedCount = 100;
+
+            // Assign
+            _server = FluentMockServer.Start();
+
+            _server
+                .Given(Request.Create()
+                    .WithPath("/foo")
+                    .UsingGet())
+                .RespondWith(Response.Create()
+                    .WithDelay(6)
+                    .WithSuccess());
+
+            int count = 0;
+            _server.LogEntriesChanged += (sender, args) => count++;
+
+            var http = new HttpClient();
+
+            // Act
+            var listOfTasks = new List<Task<HttpResponseMessage>>();
+            for (var i = 0; i < expectedCount; i++)
+            {
+                Thread.Sleep(3);
+                listOfTasks.Add(http.GetAsync(_server.Urls[0] + $"/foo"));
+            }
+            var responses = await Task.WhenAll(listOfTasks);
+            var countResponsesWithStatusNotOk = responses.Where(r => r.StatusCode != HttpStatusCode.OK).Count();
+
+            // Assert
+            Check.That(countResponsesWithStatusNotOk).Equals(0);
+            Check.That(count).Equals(expectedCount);
+        }
+
         public void Dispose()
         {
             _server?.Dispose();