Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.SpaServices.ReactDevelopmentServer;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.EntityFrameworkCore;

using Newtonsoft.Json;
using Swashbuckle.AspNetCore.Swagger;

namespace johndoeoverflow
{
  public class Startup
  {
    public Startup(IConfiguration configuration)
    {
      Configuration = configuration;
      new DatabaseContext().Database.Migrate();

    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
      services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2)
       .AddJsonOptions(options =>
      {
        options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
      });

      services.AddDbContext<DatabaseContext>();
      services.AddHealthChecks();
      // Register the Swagger generator, defining 1 or more Swagger documents
      services.AddSwaggerGen(c =>
      {
        c.SwaggerDoc("v1", new Info { Title = "My API", Version = "v1" });
      });

      // In production, the React files will be served from this directory
      services.AddSpaStaticFiles(configuration =>
      {
        configuration.RootPath = "ClientApp/build";
      });
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
      if (env.IsDevelopment())
      {
        app.UseDeveloperExceptionPage();
      }
      else
      {
        app.UseExceptionHandler("/Error");
        // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
        app.UseHsts();
      }
      app.UseHealthChecks("/health");
      app.UseHttpsRedirection();
      app.UseSwagger();

      // Enable middleware to serve swagger-ui (HTML, JS, CSS, etc.), 
      // specifying the Swagger JSON endpoint.
      app.UseSwaggerUI(c =>
      {
        c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
      });
      app.UseStaticFiles();
      app.UseSpaStaticFiles();
      app.UseMvc(routes =>
      {
        routes.MapRoute(
                  name: "default",
                  template: "{controller}/{action=Index}/{id?}");
      });

      app.UseSpa(spa =>
      {
        spa.Options.SourcePath = "ClientApp";

        if (env.IsDevelopment())
        {
          spa.UseReactDevelopmentServer(npmScript: "start");
        }
      });
    }
  }
}