fixed the issue with resources not disposed correctly (#439)

* fixed the issue with resources not disposed correctly

* disposing language service at shutdown

src/Microsoft.SqlTools.ServiceLayer/LanguageServices/BindingQueue.cs

@@ -14,7 +14,7 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
     /// <summary>
     /// Main class for the Binding Queue
     /// </summary>
-    public class BindingQueue<T> where T : IBindingContext, new()
+    public class BindingQueue<T> : IDisposable where T : IBindingContext, new()
     {
         private CancellationTokenSource processQueueCancelToken = new CancellationTokenSource();
 
@@ -313,5 +313,24 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
                 }
             }
         }
+
+        public void Dispose()
+        {
+            if (itemQueuedEvent != null)
+            {
+                itemQueuedEvent.Dispose();
+            }
+
+            if (this.BindingContextMap != null)
+            {
+                foreach (var item in this.BindingContextMap)
+                {
+                    if (item.Value != null && item.Value.ServerConnection != null && item.Value.ServerConnection.SqlConnectionObject != null)
+                    {
+                        item.Value.ServerConnection.SqlConnectionObject.Close();
+                    }
+                }
+            }
+        }
     }
 }

src/Microsoft.SqlTools.ServiceLayer/LanguageServices/LanguageService.cs

@@ -36,7 +36,7 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
     /// Main class for Language Service functionality including anything that requires knowledge of
     /// the language to perform, such as definitions, intellisense, etc.
     /// </summary>
-    public sealed class LanguageService
+    public sealed class LanguageService: IDisposable
     {
         #region Singleton Instance Implementation
 
@@ -249,6 +249,7 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
             {
                 Logger.Write(LogLevel.Verbose, "Shutting down language service");
                 DeletePeekDefinitionScripts();
+                this.Dispose();
                 await Task.FromResult(0);
             });
 
@@ -1716,5 +1717,13 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
 
             return string.Empty;
         }
+
+        public void Dispose()
+        {
+            if (bindingQueue != null)
+            {
+                bindingQueue.Dispose();
+            }
+        }
     }
 }