Program.cs

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Serilog;
using System;
using System.Threading.Tasks;

namespace opensky2cot
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var configuration = new ConfigurationBuilder()
                .SetBasePath(AppContext.BaseDirectory)
                .AddEnvironmentVariables()
                .AddCommandLine(args)
                .AddJsonFile("opensky2cot.json", optional: true)
                .Build();

            Log.Logger = new LoggerConfiguration()
                .MinimumLevel.Information()
                .Enrich.FromLogContext()
                .WriteTo.Console()
                .CreateLogger();

            await Host.CreateDefaultBuilder(args)
                .ConfigureAppConfiguration((context, builder) =>
                {
                    builder.Sources.Clear();
                    builder.AddConfiguration(configuration);
                })
                .ConfigureServices((context, services) =>
                {
                    services.AddHostedService<OpenSkyService>();
                })
                .Build()
                .RunAsync();
        }
    }
}