title: .NET Core F# project will not write to TraceSource
body: <p>I could not get my F# project to write to the TraceSource.</p>
  
  <p>Here was my F# code:</p>
  
  <pre class="lang-fs prettyprint-override"><code>use logFileStream = new FileStream("log.txt", FileMode.Append, FileAccess.Write)
  (
      use logFileListener = new TextWriterTraceListener(logFileStream)
      (
          let traceSource = TraceSource("Test", SourceLevels.All)
          traceSource.Listeners.Add(logFileListener) |&gt; ignore
          traceSource.TraceEvent(TraceEventType.Verbose, 1, "This is a test.")
      )
  )
  </code></pre>
  
  <p>Here was my F# project:</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;Project Sdk="FSharp.NET.Sdk;Microsoft.NET.Sdk"&gt;
    &lt;PropertyGroup&gt;
      &lt;OutputType&gt;Exe&lt;/OutputType&gt;
      &lt;TargetFramework&gt;netcoreapp1.1&lt;/TargetFramework&gt;
    &lt;/PropertyGroup&gt;
    &lt;ItemGroup&gt;
      &lt;Compile Include="Program.fs" /&gt;
    &lt;/ItemGroup&gt;
    &lt;ItemGroup&gt;
      &lt;PackageReference Include="FSharp.Core" Version="4.1.*" /&gt;
      &lt;PackageReference Include="FSharp.NET.Sdk" Version="1.0.*" PrivateAssets="All" /&gt;
      &lt;PackageReference Include="System.Diagnostics.TextWriterTraceListener" Version="4.3.0" /&gt;
      &lt;PackageReference Include="System.Diagnostics.Tracing" Version="4.3.0" /&gt;
    &lt;/ItemGroup&gt;
  &lt;/Project&gt;
  </code></pre>
  
  <p>Why was log.txt empty?</p>