package main
import (
	"fmt"
	"log/slog"
)
func main() {
	slog.Debug("Hello world")
	slog.Info("Hello world")
	slog.Warn("Hello world")
	slog.Error("Hello world")
	slog.Info("this is a message", "name", "zhangsan")
	age := 8
	slog.Warn(fmt.Sprintf("這是 %d 歲?", age))
}

package main
import (
	"fmt"
	"log/slog"
	"os"
	"time"
)
func main() {
	jsonLogger := slog.New(slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{
		AddSource: true,            // 添加調(diào)用源信息
		Level:     slog.LevelDebug, // 設(shè)置日志級別
		ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
			// 自定義時間格式
			if a.Key == slog.TimeKey {
				if t, ok := a.Value.Any().(time.Time); ok {
					a.Value = slog.StringValue(t.Format(time.RFC3339))
				}
			}
			// 簡化調(diào)用源信息，只保留文件名和行號
			if a.Key == slog.SourceKey {
				source := a.Value.Any().(*slog.Source)
				shortFile := source.File
				for i := len(source.File) - 1; i > 0; i-- {
					if source.File[i] == '/' {
						shortFile = source.File[i+1:]
						break
					}
				}
				return slog.String("source", fmt.Sprintf("%s:%d", shortFile, source.Line))
			}
			return a
		},
	}))
	jsonLogger.Debug("Hello world")
	jsonLogger.Info("Hello world")
	jsonLogger.Warn("Hello world")
	jsonLogger.Error("Hello world")
	jsonLogger.Info("this is a message", "name", "zhangsan")
	age := 8
	jsonLogger.Warn(fmt.Sprintf("這是 %d 歲?", age))
	// 替換默認(rèn) logger
	slog.SetDefault(jsonLogger)
	slog.Debug("Hello world")
	slog.Info("Hello world")
	slog.Warn("Hello world")
	slog.Error("Hello world")
	slog.Info("this is a message", "name", "zhangsan")
	age = 9
	slog.Warn(fmt.Sprintf("這是 %d 歲?", age))
}

package main
import (
	"fmt"
	"log/slog"
	"os"
	"time"
)
func main() {
	jsonLogger := slog.New(slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{
		AddSource: true,
		Level:     slog.LevelDebug,
		ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
			if a.Key == slog.TimeKey {
				if t, ok := a.Value.Any().(time.Time); ok {
					a.Value = slog.StringValue(t.Format(time.RFC3339))
				}
			}
			if a.Key == slog.SourceKey {
				source := a.Value.Any().(*slog.Source)
				shortFile := source.File
				for i := len(source.File) - 1; i > 0; i-- {
					if source.File[i] == '/' {
						shortFile = source.File[i+1:]
						break
					}
				}
				return slog.String("source", fmt.Sprintf("%s:%d", shortFile, source.Line))
			}
			return a
		},
	})).With("logger", "json", "env", "production")
	jsonLogger.Debug("Hello world")
	jsonLogger.Info("Hello world")
	jsonLogger.Warn("Hello world")
	jsonLogger.Error("Hello world")
	jsonLogger.Info("this is a message", "name", "zhangsan")
}

package main
import (
	"fmt"
	"log/slog"
	"os"
	"time"
)
func main() {
	jsonLogger := slog.New(slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{
		AddSource: true,
		Level:     slog.LevelDebug,
		ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
			if a.Key == slog.TimeKey {
				if t, ok := a.Value.Any().(time.Time); ok {
					a.Value = slog.StringValue(t.Format(time.RFC3339))
				}
			}
			if a.Key == slog.SourceKey {
				source := a.Value.Any().(*slog.Source)
				shortFile := source.File
				for i := len(source.File) - 1; i > 0; i-- {
					if source.File[i] == '/' {
						shortFile = source.File[i+1:]
						break
					}
				}
				return slog.String("source", fmt.Sprintf("%s:%d", shortFile, source.Line))
			}
			return a
		},
	}))
	jsonLogger = jsonLogger.With("logger", "json")
	// 使用 Group 組織相關(guān)屬性
	jsonLogger.Info("系統(tǒng)狀態(tài)",
		slog.Group("metrics",
			slog.Int("cpu", 4),
			slog.Float64("memPercent", 2.33),
		),
		slog.Group("request",
			slog.String("method", "GET"),
			slog.String("path", "/api/users"),
		),
	)
}

package main
import (
	"context"
	"log/slog"
	"os"
	"time"
)
func main() {
	jsonLogger := slog.New(slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{
		AddSource: true,
		Level:     slog.LevelDebug,
		ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
			if a.Key == slog.TimeKey {
				if t, ok := a.Value.Any().(time.Time); ok {
					a.Value = slog.StringValue(t.Format(time.RFC3339))
				}
			}
			if a.Key == slog.SourceKey {
				source := a.Value.Any().(*slog.Source)
				shortFile := source.File
				for i := len(source.File) - 1; i > 0; i-- {
					if source.File[i] == '/' {
						shortFile = source.File[i+1:]
						break
					}
				}
				return slog.String("source", fmt.Sprintf("%s:%d", shortFile, source.Line))
			}
			return a
		},
	})).With("logger", "json")
	for i := range 5 {
		jsonLogger.LogAttrs(
			context.Background(),
			slog.LevelInfo,
			"執(zhí)行遍歷",
			slog.Int("round", i),
			slog.String("task_name", "cleanup"),
			slog.Duration("duration", time.Second*time.Duration(i+1)),
		)
	}
}

package main
import (
	"context"
	"log/slog"
	"os"
)
type contextKey string
const TraceIDKey contextKey = "trace_id"
// ContextHandler 包裝一個 slog.Handler，在處理日志時自動從 context 中提取 TraceID
type ContextHandler struct {
	slog.Handler
}
func (h *ContextHandler) Handle(ctx context.Context, record slog.Record) error {
	if ctx != nil {
		if traceID, ok := ctx.Value(TraceIDKey).(string); ok && traceID != "" {
			record.AddAttrs(slog.String(string(TraceIDKey), traceID))
		}
	}
	return h.Handler.Handle(ctx, record)
}
func main() {
	baseHandler := slog.NewJSONHandler(os.Stdout, nil)
	handler := &ContextHandler{Handler: baseHandler}
	jsonLogger := slog.New(handler)
	slog.SetDefault(jsonLogger)
	ctx := context.WithValue(context.Background(), TraceIDKey, "abc123-def456")
	slog.InfoContext(ctx, "hello world")
	slog.WarnContext(ctx, "something happened", "user", "zhangsan")
}

package main
import (
	"context"
	"log/slog"
	"net"
	"net/http"
	"net/http/httputil"
	"os"
	"runtime/debug"
	"strings"
	"time"
	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
)
type contextKey string
const TraceIDKey contextKey = "trace_id"
// ContextHandler 從 context 中提取 TraceID 并添加到日志中
type ContextHandler struct {
	slog.Handler
}
func (h *ContextHandler) Handle(ctx context.Context, record slog.Record) error {
	if ctx != nil {
		if traceID, ok := ctx.Value(TraceIDKey).(string); ok && traceID != "" {
			record.AddAttrs(slog.String(string(TraceIDKey), traceID))
		}
	}
	return h.Handler.Handle(ctx, record)
}
// SlogMiddleware 是一個 Gin 中間件，用于注入 TraceID
func SlogMiddleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		start := time.Now()
		// 優(yōu)先從請求頭獲取 TraceID，沒有則生成新的
		traceID := c.GetHeader("X-Trace-ID")
		if traceID == "" {
			traceID = uuid.New().String()
		}
		// 將 TraceID 注入到標(biāo)準(zhǔn)的 context.Context 中
		// 注意：Gin 的 c.Set 只在 Gin 內(nèi)部生效，slog 需要標(biāo)準(zhǔn)庫的 Context
		ctx := context.WithValue(c.Request.Context(), TraceIDKey, traceID)
		c.Request = c.Request.WithContext(ctx)
		// 將 TraceID 寫入響應(yīng)頭，方便客戶端追蹤
		c.Header("X-Trace-ID", traceID)
		c.Next()
		// 請求結(jié)束后的匯總?cè)罩?
		slog.InfoContext(c.Request.Context(), "Request completed",
			slog.String("method", c.Request.Method),
			slog.String("path", c.Request.URL.Path),
			slog.Int("status", c.Writer.Status()),
			slog.Int("body_size", c.Writer.Size()),
			slog.Duration("latency", time.Since(start)),
		)
	}
}
// SlogRecovery 是一個自定義的恢復(fù)中間件
// 它會捕獲 Panic，記錄堆棧信息，并使用 slog.ErrorContext 輸出
func SlogRecovery() gin.HandlerFunc {
	return func(c *gin.Context) {
		defer func() {
			if err := recover(); err != nil {
				// 檢查是否是連接中斷（broken pipe）
				var brokenPipe bool
				if ne, ok := err.(*net.OpError); ok {
					if se, ok := ne.Err.(*os.SyscallError); ok {
						if strings.Contains(strings.ToLower(se.Error()), "broken pipe") ||
							strings.Contains(strings.ToLower(se.Error()), "connection reset by peer") {
							brokenPipe = true
						}
					}
				}
				// 獲取堆棧信息
				stack := string(debug.Stack())
				// 獲取原始請求內(nèi)容
				httpRequest, _ := httputil.DumpRequest(c.Request, false)
				if brokenPipe {
					slog.ErrorContext(c.Request.Context(), "網(wǎng)絡(luò)連接中斷",
						slog.Any("error", err),
						slog.String("request", string(httpRequest)),
					)
					c.Error(err.(error))
					c.Abort()
					return
				}
				// 記錄 Panic 詳情
				slog.ErrorContext(c.Request.Context(), "Recovery from panic",
					slog.Any("error", err),
					slog.String("stack", stack),
					slog.String("request", string(httpRequest)),
				)
				ctx := c.Request.Context()
				traceID, _ := ctx.Value(TraceIDKey).(string)
				// 返回 500 狀態(tài)碼
				c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{
					"code":      http.StatusInternalServerError,
					"msg":       "Internal Server Error",
					"data":      nil,
					"timestamp": time.Now().Format(time.RFC3339),
					"trace_id":  traceID,
				})
			}
		}()
		c.Next()
	}
}
func main() {
	// 初始化 slog
	baseHandler := slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
		Level: slog.LevelDebug,
	})
	handler := &ContextHandler{Handler: baseHandler}
	jsonLogger := slog.New(handler)
	slog.SetDefault(jsonLogger)
	// 使用 gin.New() 而不是 gin.Default()，避免內(nèi)置日志干擾
	r := gin.New()
	r.Use(SlogMiddleware())
	r.Use(SlogRecovery())
	r.GET("/ping", func(c *gin.Context) {
		slog.InfoContext(c.Request.Context(), "Processing /ping request",
			slog.String("user", "zhangsan"),
		)
		time.Sleep(time.Second * 2)
		c.JSON(200, gin.H{"msg": "pong"})
	})
	r.GET("/panic", func(c *gin.Context) {
		slog.InfoContext(c.Request.Context(), "About to panic")
		panic("something went wrong")
	})
	r.Run(":8080")
}

$ curl http://localhost:8080/ping
{"msg":"pong"}
$ curl http://localhost:8080/panic
{"code":500,"msg":"Internal Server Error","data":null,"timestamp":"2026-02-15T14:30:00+08:00","trace_id":"xxx-xxx-xxx"}

package main
import (
	"log/slog"
	"os"
)
func main() {
	logFile, err := os.OpenFile("app.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
	if err != nil {
		panic(err)
	}
	handler := slog.NewJSONHandler(logFile, nil)
	logger := slog.New(handler)
	slog.SetDefault(logger)
	slog.Info("hello world")
}

/path/to/app.log {
    daily
    rotate 7
    compress
    delaycompress
    missingok
    notifempty
    copytruncate    # 復(fù)制后截斷，不需要重啟 Go 程序
}

import "gopkg.in/natefinch/lumberjack.v2"
func initLumberjack() {
    rollingFile := &lumberjack.Logger{
        Filename:   "./logs/app.log",
        MaxSize:    100, // 單位 MB
        MaxBackups: 3,   // 保留舊文件的最大個數(shù)
        MaxAge:     28,  // 保留舊文件的最大天數(shù)
        Compress:   true, // 是否壓縮
    }
    handler := slog.NewJSONHandler(rollingFile, nil)
    slog.SetDefault(slog.New(handler))
}

package main
import (
	"log/slog"
	"os"
)
func main() {
	logFile, err := os.OpenFile("app.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
	if err != nil {
		panic(err)
	}
	fileHandler := slog.NewJSONHandler(logFile, nil)
	consoleHandler := slog.NewTextHandler(os.Stdout, nil)
	multiHandler := slog.NewMultiHandler(fileHandler, consoleHandler) // slog.NewMultiHandler 需要go1.26.0+版本
	logger := slog.New(multiHandler)
	slog.SetDefault(logger)
	slog.Info("hello world")
}

package main
import (
	"log/slog"
	"os"
)
func main() {
	// 定義自定義日志級別
	const (
		LevelTrace   = slog.Level(-8) // 比 Debug 更低
		LevelNotice  = slog.Level(2)  // 介于 Info 和 Warn 之間
		LevelFatal   = slog.Level(12) // 比 Error 更高
	)
	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
		Level: LevelTrace, // 設(shè)置最低級別
	}))
	logger.Log(nil, LevelTrace, "trace message")
	logger.Log(nil, LevelNotice, "notice message")
	logger.Log(nil, LevelFatal, "fatal message")
}