问单例ImplementationType:尝试激活时无法解析'Nest.IElasticClient‘类型的服务

EN

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

    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.AddControllers();
            services.AddSingleton<IProductService, ESProductService>();
            services.Configure<ProductSettings>(Configuration.GetSection("product"));
            services.AddElasticsearch(Configuration);
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

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

public static class ElasticsearchExtensions
    {
        public static void AddElasticsearch(this IServiceCollection services, IConfiguration configuration)
        {
            var url = configuration["elasticsearch:url"];
            var defaultIndex = configuration["elasticsearch:index"];

            var settings = new ConnectionSettings(new Uri(url))
                .DefaultIndex(defaultIndex);

            AddDefaultMappings(settings);

            var client = new ElasticClient(settings);

            services.AddSingleton(client);

            CreateIndex(client, defaultIndex);
        }

        private static void AddDefaultMappings(ConnectionSettings settings)
        {
            settings
                .DefaultMappingFor<Product>(m => m
                .Ignore(p => p.Price)
                .Ignore(p => p.Quantity)
                .Ignore(p => p.Rating)
            );
        }

        private static void CreateIndex(IElasticClient client, string indexName)
        {
            var createIndexResponse = client.Indices.Create(indexName,
                index => index.Map<Product>(x => x.AutoMap())
            );
        }
    }