title: Issue running IdentityServer4
body: <p>I am learning about the IdentityServer4 <a href="https://identityserver4.readthedocs.io/en/release/quickstarts/0_overview.html" rel="noreferrer">https://identityserver4.readthedocs.io/en/release/quickstarts/0_overview.html</a> but seem to be having issues getting it working.</p>
  
  <p>After creating the API section of the project and configured accordingly:</p>
  
  <pre><code>public void Configure(IApplicationBuilder app, ILoggerFactory loggerFactory)
          {
              loggerFactory.AddConsole(Configuration.GetSection("Logging"));
              loggerFactory.AddDebug();
  
              app.UseIdentityServerAuthentication(new IdentityServerAuthenticationOptions
              {
                  Authority = "http://localhost:5000",
                  RequireHttpsMetadata = false,
  
                  ApiName = "api1"
              });
  
              app.UseMvc();
          }
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>'IApplicationBuilder' does not contain a definition for 'UseIdentityServerAuthentication' and no extension method 'UseIdentityServerAuthentication' accepting a first argument of type 'IApplicationBuilder' could be found (are you missing a using directive or an assembly reference?)
  </code></pre>
  
  <p>Any advice what i am missing here?</p>
  
  <p>EDIT 1:
  I've noticed i cannot reference the namespace either even tho the package is installed and present.</p>
  
  <p>i.e.</p>
  
  <pre><code>using IdentityServer4.AccessTokenValidation;
  </code></pre>
  
  <p>or</p>
  
  <pre><code>using IdentityServer4;
  </code></pre>