add DisconnectAsync

Author: doghappy

src/SocketIOClient/V2/SocketIO.cs

@@ -190,4 +190,11 @@ private void HandlePongMessage(IMessage message)
         var pong = (PongMessage)message;
         OnPong?.Invoke(this, pong.Duration);
     }
+
+    public async Task DisconnectAsync()
+    {
+        _session?.Dispose();
+        Connected = false;
+        Id = null;
+    }
 }

tests/SocketIOClient.UnitTests/V2/SocketIOTests.cs

@@ -273,4 +273,25 @@ await _io.OnNextAsync(new PongMessage
 
         ts.Should().Be(TimeSpan.FromSeconds(2));
     }
+
+    [Fact]
+    public async Task DisconnectAsync_NeverConnected_ClearStatefulData()
+    {
+        await _io.DisconnectAsync();
+
+        _io.Connected.Should().BeFalse();
+        _io.Id.Should().BeNull();
+        _session.DidNotReceive().Dispose();
+    }
+
+    [Fact]
+    public async Task DisconnectAsync_EverConnected_ClearStatefulData()
+    {
+        await ConnectAsync();
+        await _io.DisconnectAsync();
+
+        _io.Connected.Should().BeFalse();
+        _io.Id.Should().BeNull();
+        _session.Received(1).Dispose();
+    }
 }