Program.cs

using LibraryManagementSystem;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using System;
using System.IO;

namespace YourAppName
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureAppConfiguration((hostingContext, config) =>
                {
                    config.SetBasePath(Directory.GetCurrentDirectory());
                    config.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true);
                    config.AddJsonFile($"appsettings.{hostingContext.HostingEnvironment.EnvironmentName}.json", optional: true, reloadOnChange: true);
                    config.AddEnvironmentVariables();
                    if (args != null)
                    {
                        config.AddCommandLine(args);
                    }
                })
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });
    }
}