c# 9 syntax improvement with Program.cs

src/cartservice/Program.cs

@@ -12,26 +12,15 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-using System;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.Hosting;
+using cartservice;
 
-namespace cartservice
-{
-    public class Program
-    {
-        public static void Main(string[] args)
-        {
-            CreateHostBuilder(args).Build().Run();
-        }
+CreateHostBuilder(args).Build().Run();
 
-        // Additional configuration is required to successfully run gRPC on macOS.
-        // For instructions on how to configure Kestrel and gRPC clients on macOS, visit https://go.microsoft.com/fwlink/?linkid=2099682
-        public static IHostBuilder CreateHostBuilder(string[] args) =>
-            Host.CreateDefaultBuilder(args)
-                .ConfigureWebHostDefaults(webBuilder =>
-                {
-                    webBuilder.UseStartup<Startup>();
-                });
-    }
-}
+static IHostBuilder CreateHostBuilder(string[] args) =>
+    Host.CreateDefaultBuilder(args)
+        .ConfigureWebHostDefaults(webBuilder =>
+        {
+            webBuilder.UseStartup<Startup>();
+        });