feat(backend): Go 服务骨架（配置、日志、数据库、中间件、Wire）

- config: Viper YAML 配置 + 环境变量覆盖
- logs: zap 结构化日志 + trace_id 链路追踪 + 敏感信息脱敏
- db: PostgreSQL (GORM) + Redis (go-redis) 连接管理
- middleware: Trace/Logger/CORS/Recovery 四层中间件
- provider: Wire 编译时依赖注入
- main.go: 优雅启动/关闭 HTTP 服务

Made-with: Cursor

backend/go-service/pkg/db/postgres.go

@@ -0,0 +1,93 @@
+// Package db 提供数据库连接管理
+package db
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/echochat/backend/config"
+	"github.com/echochat/backend/pkg/logs"
+	"go.uber.org/zap"
+	"gorm.io/driver/postgres"
+	"gorm.io/gorm"
+	"gorm.io/gorm/logger"
+)
+
+// GormDB 全局 GORM 数据库实例
+var GormDB *gorm.DB
+
+// zapGormLogger 将 GORM 日志适配到 zap
+type zapGormLogger struct{}
+
+func (l *zapGormLogger) LogMode(logger.LogLevel) logger.Interface { return l }
+
+func (l *zapGormLogger) Info(ctx context.Context, msg string, data ...interface{}) {
+	logs.Info(ctx, "gorm", fmt.Sprintf(msg, data...))
+}
+
+func (l *zapGormLogger) Warn(ctx context.Context, msg string, data ...interface{}) {
+	logs.Warn(ctx, "gorm", fmt.Sprintf(msg, data...))
+}
+
+func (l *zapGormLogger) Error(ctx context.Context, msg string, data ...interface{}) {
+	logs.Error(ctx, "gorm", fmt.Sprintf(msg, data...))
+}
+
+func (l *zapGormLogger) Trace(ctx context.Context, begin time.Time, fc func() (sql string, rowsAffected int64), err error) {
+	elapsed := time.Since(begin)
+	sql, rows := fc()
+	fields := []zap.Field{
+		zap.Duration("latency", elapsed),
+		zap.Int64("rows", rows),
+		zap.String("sql", sql),
+	}
+	if err != nil {
+		fields = append(fields, zap.Error(err))
+		logs.Error(ctx, "gorm.trace", "SQL执行失败", fields...)
+		return
+	}
+	if elapsed > 200*time.Millisecond {
+		logs.Warn(ctx, "gorm.trace", "慢SQL告警", fields...)
+		return
+	}
+	logs.Debug(ctx, "gorm.trace", "SQL执行", fields...)
+}
+
+// NewPostgres 初始化 PostgreSQL 数据库连接
+func NewPostgres(cfg *config.DatabaseConfig) (*gorm.DB, error) {
+	funcName := "db.NewPostgres"
+	ctx := context.Background()
+
+	logs.Info(ctx, funcName, "正在连接 PostgreSQL",
+		zap.String("host", cfg.Host),
+		zap.Int("port", cfg.Port),
+		zap.String("dbname", cfg.DBName),
+	)
+
+	db, err := gorm.Open(postgres.Open(cfg.DSN()), &gorm.Config{
+		Logger: &zapGormLogger{},
+	})
+	if err != nil {
+		logs.Error(ctx, funcName, "PostgreSQL 连接失败", zap.Error(err))
+		return nil, fmt.Errorf("连接 PostgreSQL 失败: %w", err)
+	}
+
+	sqlDB, err := db.DB()
+	if err != nil {
+		return nil, fmt.Errorf("获取底层 sql.DB 失败: %w", err)
+	}
+
+	sqlDB.SetMaxIdleConns(cfg.MaxIdleConns)
+	sqlDB.SetMaxOpenConns(cfg.MaxOpenConns)
+	sqlDB.SetConnMaxLifetime(time.Hour)
+
+	if err := sqlDB.Ping(); err != nil {
+		logs.Error(ctx, funcName, "PostgreSQL Ping 失败", zap.Error(err))
+		return nil, fmt.Errorf("ping PostgreSQL 失败: %w", err)
+	}
+
+	GormDB = db
+	logs.Info(ctx, funcName, "PostgreSQL 连接成功")
+	return db, nil
+}