Startup.cs

public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
        }

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseMvcWithDefaultRoute();

            app.Run(async (context) =>
            {
                await context.Response.WriteAsync("Hello World!");
            });
        }
    }