#152 conditionalise dependencies (#153)

* #152 conditionalise dependencies

* Update Websocket.Client.csproj

Author: thompson-tomo

src/Websocket.Client/Websocket.Client.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
 	<PropertyGroup>
 		<TargetFrameworks>netstandard2.1;net6;net7;net8</TargetFrameworks>
@@ -31,6 +31,9 @@
 		<PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="8.0.0" />
 		<PackageReference Include="Microsoft.IO.RecyclableMemoryStream" Version="3.0.0" />
 		<PackageReference Include="System.Reactive" Version="6.0.0" />
+	</ItemGroup>
+
+	<ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.1'">
 		<PackageReference Include="System.Threading.Channels" Version="8.0.0" />
 	</ItemGroup>