Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using NewsApp.Services;

namespace NewsApp
{
    public class Startup
    {
        public IConfiguration Configuration {get; set;}

        public Startup(IHostingEnvironment env)
        {
            var builder = new ConfigurationBuilder()
            .SetBasePath(env.ContentRootPath)
            .AddJsonFile("appsettings.json");

            Configuration = builder.Build();    
        }

        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddSingleton(implementation => Configuration);
            services.AddSingleton<IGreeter, Greeter>();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory, IGreeter greeter)
        {
            loggerFactory.AddConsole();

            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseFileServer();
            
            app.Run(async (context) =>
            {
//                throw new Exception("Error");

                var greeting = greeter.GetGreeting();
                await context.Response.WriteAsync(greeting);
            });
        }
    }
}