Add gRPC client module and its corresponding test case

Client/Assets/Scripts/Network/GrpcClient.cs

@@ -0,0 +1,48 @@
+using System.Net.Http;
+using System.Threading.Tasks;
+using Grpc.Net.Client;
+using Grpc.Net.Client.Web;
+using Protocol;
+using Utils;
+
+namespace Network
+{
+    public class GrpcClient : Singleton<GrpcClient>
+    {
+        // The address must adopt HTTP.
+        private const string ServerAddress = "http://127.0.0.1:12345";
+
+        private readonly GrpcChannel _channel;
+        private readonly GameService.GameServiceClient _game;
+        private readonly GeneralService.GeneralServiceClient _general;
+
+        public GrpcClient()
+        {
+            var httpHandler = new GrpcWebHandler(GrpcWebMode.GrpcWeb, new HttpClientHandler());
+            var channelOptions = new GrpcChannelOptions
+            {
+                HttpHandler = httpHandler
+            };
+
+            _channel = GrpcChannel.ForAddress(ServerAddress, channelOptions);
+
+            _general = new GeneralService.GeneralServiceClient(_channel);
+            _game = new GameService.GameServiceClient(_channel);
+        }
+
+        ~GrpcClient()
+        {
+            _channel.ShutdownAsync().Wait();
+        }
+
+        public async Task<ServerInfo> GetServerInfo()
+        {
+            return await _general.GetServerInfoAsync(new Empty());
+        }
+
+        public async Task<LoginResponse> Login(string username, string password)
+        {
+            return await _game.LoginAsync(new LoginRequest { Username = username, Password = password });
+        }
+    }
+}