Startup.cs

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
    services.AddAuthentication()
        .AddJwtBearer(options =>
        {
            // The API resource scope issued in authorization server
            options.Audience = "resource.server.api";
            // URL of my authorization server
            options.Authority = "https://localhost:44357";
        });

    // Making JWT authentication scheme the default
    services.AddAuthorization(options =>
    {
        options.DefaultPolicy = new AuthorizationPolicyBuilder(JwtBearerDefaults.AuthenticationScheme)
            .RequireAuthenticatedUser()
            .Build();
    });
}