Fixing ssl client shutdown

Author: chronoxor

.appveyor.yml

@@ -1,5 +1,5 @@
 # Specify version format
-version: "1.7.0.{build}"
+version: "1.8.0.{build}"
 
 # Image to use
 image: Visual Studio 2019

source/NetCoreServer/NetCoreServer.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>netstandard2.1</TargetFramework>
-    <Version>1.7.0</Version>
+    <Version>1.8.0</Version>
     <Authors>Ivan Shynkarenka</Authors>
     <Copyright>Copyright (c) 2019 Ivan Shynkarenka</Copyright>
     <RepositoryUrl>https://github.com/chronoxor/NetCoreServer</RepositoryUrl>

source/NetCoreServer/SslClient.cs

@@ -1,4 +1,5 @@
 using System;
+using System.IO;
 using System.Net;
 using System.Net.Security;
 using System.Net.Sockets;