Avoiding non-observed Task exceptions

Author: darkl

src/net45/WampSharp/WAMP2/V2/Client/Session/IWampSessionClientExtended.cs

@@ -14,9 +14,7 @@ internal interface IWampSessionClientExtended :
 
         Task OpenTask { get; }
 
-        Task<GoodbyeMessage> CloseTask { get; }
-
-        void Close(string reason, GoodbyeDetails details);
+        Task<GoodbyeMessage> Close(string reason, GoodbyeDetails details);
 
         void OnConnectionOpen();
         void OnConnectionClosed();

src/net45/WampSharp/WAMP2/V2/Client/Session/WampSessionClient.cs

@@ -16,7 +16,7 @@ public class WampSessionClient<TMessage> : IWampSessionClientExtended,
         private static readonly AuthenticateExtraData EmptyAuthenticateDetails = new AuthenticateExtraData();
         private readonly IWampServerProxy mServerProxy;
         private TaskCompletionSource<bool> mOpenTask = new TaskCompletionSource<bool>();
-        private TaskCompletionSource<GoodbyeMessage> mCloseTask = new TaskCompletionSource<GoodbyeMessage>();
+        private TaskCompletionSource<GoodbyeMessage> mCloseTask;
         private readonly IWampFormatter<TMessage> mFormatter;
         private bool mGoodbyeSent;
 		private readonly IWampClientAuthenticator mAuthenticator;
@@ -118,7 +118,7 @@ public void Goodbye(GoodbyeDetails details, string reason)
                 else
                 {
                     GoodbyeMessage message = new GoodbyeMessage(){Details = details, Reason = reason};
-                    mCloseTask.SetResult(message);
+                    mCloseTask?.SetResult(message);
                 }
             }
 
@@ -135,7 +135,7 @@ private void RaiseConnectionBroken()
 
             Interlocked.CompareExchange(ref mIsConnected, 0, 1);
             mOpenTask = new TaskCompletionSource<bool>();
-            mCloseTask = new TaskCompletionSource<GoodbyeMessage>();
+            mCloseTask = null;
             mCloseEventArgs = null;
 
             OnConnectionBroken(closeEventArgs);
@@ -160,15 +160,20 @@ private void TrySetCloseEventArgs(SessionCloseType sessionCloseType,
 
         public Task OpenTask => mOpenTask.Task;
 
-        public Task<GoodbyeMessage> CloseTask => mCloseTask.Task;
-
-        public void Close(string reason, GoodbyeDetails details)
+        public Task<GoodbyeMessage> Close(string reason, GoodbyeDetails details)
         {
             reason = reason ?? WampErrors.CloseNormal;
             details = details ?? EmptyGoodbyeDetails;
 
+            TaskCompletionSource<GoodbyeMessage> closeTask = 
+                new TaskCompletionSource<GoodbyeMessage>();
+
+            mCloseTask = closeTask;
+
             mGoodbyeSent = true;
             mServerProxy.Goodbye(details, reason);
+
+            return closeTask.Task;
         }
 
         public void OnConnectionOpen()

src/net45/WampSharp/WAMP2/V2/Client/WampChannel.cs

@@ -73,9 +73,7 @@ public void Close()
 
         public Task<GoodbyeMessage> Close(string reason, GoodbyeDetails details)
         {
-            Task<GoodbyeMessage> task = mClient.CloseTask;
-            mClient.Close(reason, details);
-            return task;
+            return mClient.Close(reason, details);
         }
     }
 }

src/net45/WampSharp/WAMP2/V2/Client/WampClient.cs

@@ -57,8 +57,6 @@ public WampClient(IWampRealmProxyFactory<TMessage> realmFactory)
 
         public Task OpenTask => SessionClient.OpenTask;
 
-        public Task<GoodbyeMessage> CloseTask => SessionClient.CloseTask;
-
         public void Challenge(string authMethod, ChallengeDetails extra)
         {
             SessionClient.Challenge(authMethod, extra);
@@ -81,9 +79,9 @@ public void Goodbye(GoodbyeDetails details, string reason)
 
         public long Session => SessionClient.Session;
 
-        public void Close(string reason, GoodbyeDetails details)
+        public Task<GoodbyeMessage> Close(string reason, GoodbyeDetails details)
         {
-            SessionClient.Close(reason, details);
+            return SessionClient.Close(reason, details);
         }
 
         public void OnConnectionOpen()