IdentityServer4 Keyset is missing报错

IdentityServer4 Keyset is missing报错

一直很懒没有记录学习过程中发现的问题，希望以后自己能多记录这些过程。

由于自己英文很渣，一般都是边写边用翻译软件翻译，当看到AddDeveloperSigningCredential时就不淡定了，以为是开发时用的临时证书生成语句，结果就把它Delete了，哪成想一运行报错。
ERROR|Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware|An unhandled exception has occurred while executing the request. System.InvalidOperationException: Policy error while contacting the discovery endpoint http://localhost:5000/.well-known/openid-configuration: Keyset is missing
估计没几个人会像我这样写代码，一般都是照抄，我有洁癖喜欢把用不到的代码都清理掉，结果在中文网站上愣是没找到解决办法，最后终于在https://*.com/questions/47709265/identity-server-4-error-keyset-is-missing上找到这个问题。哎！！
下面是代码，记录一下。

public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddDbContext<ArchivesContext>(options => {
                var connectionString = Configuration.GetConnectionString("Connection");
                options.UseMySQL(connectionString);
            });
            services.AddScoped<IArchivesRepository, ArchivesRepository>();
            services.AddIdentityServer()
                .AddDeveloperSigningCredential()
                .AddInMemoryIdentityResources(Resources.GetIdentityResourceResources())
                .AddInMemoryApiResources(Resources.GetApiResources())
                .AddInMemoryClients(Clients.GetClients())
                .AddResourceOwnerValidator<ResourceOwnerPasswordValidator>();

            services.AddAuthentication(IdentityServerAuthenticationDefaults.AuthenticationScheme)
                .AddIdentityServerAuthentication(options =>
                {
                    options.Authority = $"http://{Configuration["Identity:IP"]}:{Configuration["Identity:Port"]}";
                    options.RequireHttpsMetadata = false;
                    options.ApiName = "WebApi";
                    options.ApiSecret = "DAWebApi";
                });
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseIdentityServer();
            
            app.UseMvc();
        }
    }