title: Fail: Microsoft.AspNetCore.SpaServices[0]
body: <p>Asp.net core 2.1 +Angular 6 application. In my <code>Start.cs</code> file. we have</p>
  
  <pre><code>app.UseSpa(spa =&gt;
          {
              // To learn more about options for serving an Angular SPA from ASP.NET Core,
              // see https://go.microsoft.com/fwlink/?linkid=864501
  
              spa.Options.SourcePath = "ClientApp";
  
              if (env.IsDevelopment())
              {
                  spa.UseAngularCliServer(npmScript: "start");
              }
          });
  </code></pre>
  
  <p>In the morning, I run the asp.net core application from Visual Studio(click F5). I got webpack build stuck on build module. It build a scss file for a long time and hangs there. So the web page throws asp.net core middleware exception.</p>
  
  <p>However in the afternoon, I got a different error. Which is <code>Fail: Microsoft.AspNetCore.SpaServices[0]</code>.</p>
  
  <p>However if I run <code>npm start</code> in command window, then run <code>dotnet run</code> in Visual Studio code. It is fine. </p>
  
  <p>Tell me what to do?</p>