I am configuring net core web api using 3.1 version. I already checked this question here but no one of answers worked with my case.
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I try to configure web api with net core ver 3.1. Another app with simmiliar configuration and same version of packages works as well with same iis express on my pc.

Here is my `Startup.cs`

```
public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }
        public IConfiguration Configuration { get; }
        readonly string AllowSpecificOrigins = "_allowSpecificOrigins";

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddCors(options =>
            {
                options.AddPolicy(AllowSpecificOrigins,
                builder =>
                {
                    builder.AllowCredentials().AllowAnyMethod().AllowAnyHeader().WithOrigins("http://localhost:4200");
                });
            });

            services.AddControllers()
                .AddNewtonsoftJson();

            services.AddScoped<IAccountRepository, AccountRepository>();
            services.AddScoped<IDocsRepository, DocsRepository>();

            services.AddDbContext<LibContext>(options =>
                options.UseNpgsql(Configuration.GetConnectionString("LibraryDatabase"), x => x.UseNetTopologySuite()));

            services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
                .AddJwtBearer(options =>
                {
                    options.RequireHttpsMetadata = false; 
                    options.TokenValidationParameters = new TokenValidationParameters
                    {
                        ValidateIssuer = true,
                        ValidIssuer = AuthOptions.ISSUER,
                        ValidateAudience = true,
                        ValidAudience = AuthOptions.AUDIENCE,
                        ValidateLifetime = true,
                        IssuerSigningKey = AuthOptions.GetSymmetricSecurityKey(),
                        ValidateIssuerSigningKey = true
                    };                  
                });
            services.AddIdentity<ApplicationUser, IdentityRole>(options =>
            {
                //password settings
                options.Password.RequiredLength = 8;
                options.Password.RequireNonAlphanumeric = false;

                options.User.RequireUniqueEmail = true;

                //lockout settings
                options.Lockout.AllowedForNewUsers = true;
                options.Lockout.DefaultLockoutTimeSpan = TimeSpan.FromMinutes(5);
                options.Lockout.MaxFailedAccessAttempts = 5;
            })
                .AddEntityFrameworkStores<LibContext>()
                .AddUserManager<UserManager<ApplicationUser>>()
                .AddDefaultTokenProviders();

            services.AddSignalR();

        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            app.UseCors(AllowSpecificOrigins); //DEV MODE!           
            app.UseStaticFiles();
            app.UseStaticFiles(new StaticFileOptions()
            {
                FileProvider = new PhysicalFileProvider(Path.Combine(Directory.GetCurrentDirectory(), @"Library")),
                RequestPath = new PathString("/Library")
            });
            app.UseRouting();
            app.UseAuthentication();
            app.UseAuthorization();
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();                
            });
        }
    }

```

Seems like i got no typos in my `appsettings.json`

```
{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "LibraryDatabase": "Host=localhost;Port=5432;Database=librarydb;Username=postgres;Password=mypasshere"
  }
}

```

My `app.csproj`

```
<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <Folder Include="Library\" />
  </ItemGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="3.1.3" />
    <PackageReference Include="Microsoft.AspNetCore.Identity.EntityFrameworkCore" Version="3.1.3" />
    <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="3.1.3" />
    <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="2.2.0" />
    <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL.NetTopologySuite" Version="2.2.0" />
    <PackageReference Include="ProjNET4GeoAPI" Version="1.4.1" />
  </ItemGroup>

</Project>

```

Event viewer throw 2 errors, but i cant figure out what is wrong. Errors:

> 
> Application '/LM/W3SVC/2/ROOT' with physical root '**my app folder**' has exited from Program.Main with exit code = '0'. First 30KB characters of captured stdout and stderr logs:
>  Programm starts
> 
> 
> Application '/LM/W3SVC/2/ROOT' with physical root '**my app folder**' failed to load coreclr. Exception message:
>  CLR worker thread exited prematurely
> 
> 
> 

Thanks for your time
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