Program.cs

using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.IdentityModel.Tokens;
using System.Text;
using React.AspNet;
using JavaScriptEngineSwitcher.Extensions.MsDependencyInjection;
using JavaScriptEngineSwitcher.V8;
using Microsoft.AspNetCore.Cors.Infrastructure;

namespace Coals_WebApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var builder = WebApplication.CreateBuilder(args);
            // Add services to the container.
            builder.Services.AddCors(options =>
            {
                options.AddDefaultPolicy(
                                  policy =>
                                  {
                                      policy.WithOrigins("http://localhost:3000")
                                      .AllowAnyHeader()
                                      .AllowAnyMethod(); // add the allowed origins
                                  });
            });
            builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme).AddJwtBearer(options =>
            {
                options.TokenValidationParameters = new TokenValidationParameters()
                {
                    ValidateIssuer = true,
                    ValidIssuer = AuthOptions.ISSUER,
                    ValidateAudience = true,
                    ValidAudience = AuthOptions.AUDIENCE,
                    ValidateLifetime = true,
                    IssuerSigningKey = AuthOptions.GetSymmetricSecurityKey(),
                    ValidateIssuerSigningKey = true
                };
            });


            builder.Services.AddAuthorization();
            builder.Services.AddControllersWithViews();
            builder.Services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
            builder.Services.AddReact();
            builder.Services.AddJsEngineSwitcher(options => options.DefaultEngineName = V8JsEngine.EngineName).AddV8();

            var app = builder.Build();

            app.UseAuthentication();
            app.UseAuthorization();
            // Configure the HTTP request pipeline.
            if (!app.Environment.IsDevelopment())
            {
                app.UseExceptionHandler("/Home/Error");
            }
            

            app.UseReact(config =>
            {

            });
            app.UseStaticFiles();
            
            app.UseRouting();

            app.UseCors();
            app.UseAuthorization();

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

            app.Run();
        }
        public class AuthOptions
        {
            public const string ISSUER = "Me";
            public const string AUDIENCE = "People";
            const string KEY = "mysupersecret_secretkey!123";
            public static SymmetricSecurityKey GetSymmetricSecurityKey() => new SymmetricSecurityKey(Encoding.UTF8.GetBytes(KEY));
        }
    }
}