Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Newtonsoft.Json;
using tree_api.Interfaces;
using tree_api.Services;

namespace tree_api {
    public class Startup {
        public Startup (IConfiguration configuration) {
            Configuration = configuration;
        }

        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.AddScoped<JsonSerializerSettings> (x => new JsonSerializerSettings { ReferenceLoopHandling = ReferenceLoopHandling.Error, Formatting = Formatting.Indented });
            services.AddScoped<IJsonService, JsonService> ();
            services.AddScoped<IStorageService, StorageService> ();

            services.AddControllers ();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure (IApplicationBuilder app, IWebHostEnvironment env) {
            if (env.IsDevelopment ()) {
                app.UseDeveloperExceptionPage ();
            }

            app.UseHttpsRedirection ();

            app.UseRouting ();

            app.UseAuthorization ();

            app.UseEndpoints (endpoints => {
                endpoints.MapControllers ();
            });
        }
    }
}