refactor: 重构trustlog-sdk目录结构到trustlog/go-trustlog

- 将所有trustlog-sdk文件移动到trustlog/go-trustlog/目录
- 更新README中所有import路径从trustlog-sdk改为go-trustlog
- 更新cookiecutter配置文件中的项目名称
- 更新根目录.lefthook.yml以引用新位置的配置
- 添加go.sum文件到版本控制
- 删除过时的示例文件

这次重构与trustlog-server保持一致的目录结构，
为未来支持多语言SDK（Python、Java等）预留空间。

internal/grpcclient/loadbalancer_test.go

@@ -0,0 +1,186 @@
+package grpcclient_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+
+	"go.yandata.net/iod/iod/trustlog-sdk/internal/grpcclient"
+)
+
+// mockClient 用于测试的模拟客户端.
+type mockClient struct {
+	ID string
+}
+
+func TestNewLoadBalancer(t *testing.T) {
+	tests := []struct {
+		name     string
+		addrs    []string
+		dialOpts []grpc.DialOption
+		wantErr  bool
+		errMsg   string
+	}{
+		{
+			name: "成功创建负载均衡器",
+			addrs: []string{
+				"localhost:9090",
+				"localhost:9091",
+			},
+			dialOpts: []grpc.DialOption{
+				grpc.WithTransportCredentials(insecure.NewCredentials()),
+			},
+			wantErr: false,
+		},
+		{
+			name:     "没有地址应该失败",
+			addrs:    []string{},
+			dialOpts: nil,
+			wantErr:  true,
+			errMsg:   "at least one server address is required",
+		},
+		{
+			name:     "nil地址列表应该失败",
+			addrs:    nil,
+			dialOpts: nil,
+			wantErr:  true,
+			errMsg:   "at least one server address is required",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			lb, err := grpcclient.NewLoadBalancer(
+				tt.addrs,
+				tt.dialOpts,
+				func(_ grpc.ClientConnInterface) *mockClient {
+					return &mockClient{ID: "test"}
+				},
+			)
+
+			if tt.wantErr {
+				require.Error(t, err)
+				if tt.errMsg != "" {
+					assert.Contains(t, err.Error(), tt.errMsg)
+				}
+				assert.Nil(t, lb)
+			} else {
+				// 注意：这里会实际尝试连接，在测试环境下可能失败
+				// 实际使用时应该使用 mock 或 bufconn
+				if err != nil {
+					t.Skipf("Skipping test - cannot connect to servers: %v", err)
+					return
+				}
+				require.NoError(t, err)
+				require.NotNil(t, lb)
+				assert.Equal(t, len(tt.addrs), lb.ServerCount())
+				// 清理
+				_ = lb.Close()
+			}
+		})
+	}
+}
+
+func TestLoadBalancer_Next(t *testing.T) {
+	// 创建一个模拟的负载均衡器，不需要真实连接
+	t.Run("轮询算法测试", func(t *testing.T) {
+		// 这个测试需要使用 bufconn 或其他 mock 方式
+		// 暂时跳过需要真实连接的测试
+		if testing.Short() {
+			t.Skip("Skipping test that requires network connection")
+		}
+
+		addrs := []string{"localhost:9090", "localhost:9091", "localhost:9092"}
+		lb, err := grpcclient.NewLoadBalancer(
+			addrs,
+			[]grpc.DialOption{grpc.WithTransportCredentials(insecure.NewCredentials())},
+			func(_ grpc.ClientConnInterface) *mockClient {
+				return &mockClient{ID: "test"}
+			},
+		)
+		if err != nil {
+			t.Skipf("Cannot create load balancer: %v", err)
+			return
+		}
+		defer lb.Close()
+
+		// 测试轮询：调用 Next() 多次应该轮询返回不同的客户端
+		clients := make([]*mockClient, 6)
+		for i := range 6 {
+			clients[i] = lb.Next()
+			assert.NotNil(t, clients[i])
+		}
+	})
+}
+
+func TestLoadBalancer_Close(t *testing.T) {
+	if testing.Short() {
+		t.Skip("Skipping test that requires network connection")
+	}
+
+	addrs := []string{"localhost:9090"}
+	lb, err := grpcclient.NewLoadBalancer(
+		addrs,
+		[]grpc.DialOption{grpc.WithTransportCredentials(insecure.NewCredentials())},
+		func(_ grpc.ClientConnInterface) *mockClient {
+			return &mockClient{ID: "test"}
+		},
+	)
+	if err != nil {
+		t.Skipf("Cannot create load balancer: %v", err)
+		return
+	}
+
+	// 第一次关闭
+	err = lb.Close()
+	require.NoError(t, err)
+
+	// 再次关闭应该也不会报错
+	err = lb.Close()
+	assert.NoError(t, err)
+}
+
+func TestLoadBalancer_ServerCount(t *testing.T) {
+	if testing.Short() {
+		t.Skip("Skipping test that requires network connection")
+	}
+
+	tests := []struct {
+		name      string
+		addrs     []string
+		wantCount int
+	}{
+		{
+			name:      "单服务器",
+			addrs:     []string{"localhost:9090"},
+			wantCount: 1,
+		},
+		{
+			name:      "多服务器",
+			addrs:     []string{"localhost:9090", "localhost:9091", "localhost:9092"},
+			wantCount: 3,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			lb, err := grpcclient.NewLoadBalancer(
+				tt.addrs,
+				[]grpc.DialOption{grpc.WithTransportCredentials(insecure.NewCredentials())},
+				func(_ grpc.ClientConnInterface) *mockClient {
+					return &mockClient{ID: "test"}
+				},
+			)
+			if err != nil {
+				t.Skipf("Cannot create load balancer: %v", err)
+				return
+			}
+			defer lb.Close()
+
+			assert.Equal(t, tt.wantCount, lb.ServerCount())
+		})
+	}
+}