fix(logging,mimeutil,variable): correct data corruption and behavior bugs

- logging: pre-allocate fresh slice for request field to avoid mutating
  fasthttp internal buffers via append into slices with excess capacity
- mimeutil: move defaultMIME fallback before cache insertion so unknown
  extensions are consistently cached as application/octet-stream
- builtin: use -0700 timezone format instead of hardcoded +0800; cache
  generated request_id in UserValue to prevent different IDs per expansion
- variable: initialize maps in fallback Context to prevent nil map panic

internal/logging/logging.go

@@ -142,9 +142,15 @@ func getOutput(path string) io.Writer {
 func (l *Logger) LogAccess(ctx *fasthttp.RequestCtx, status int, size int64, duration time.Duration) {
 	// JSON 格式或空格式：输出结构化 JSON
 	if l.accessFormat == formatJSON || l.accessFormat == "" {
+		method := ctx.Method()
+		path := ctx.Path()
+		req := make([]byte, 0, len(method)+1+len(path))
+		req = append(req, method...)
+		req = append(req, ' ')
+		req = append(req, path...)
 		l.accessLog.Info().
 			Str("remote_addr", netutil.FormatRemoteAddr(ctx)).
-			Bytes("request", append(append(ctx.Method(), ' '), ctx.Path()...)).
+			Bytes("request", req).
 			Int("status", status).
 			Int64("body_bytes_sent", size).
 			Dur("request_time", duration).

internal/mimeutil/detect.go

@@ -146,16 +146,17 @@ func DetectContentType(filePath string) string {
 		}
 	}
 
-	// 插入新条目
+	// 未知扩展名回退到默认值
-	entry := &mimeCacheEntry{ext: ext, mimeType: mimeType}
-	entry.element = mimeLRU.PushFront(entry)
-	mimeCache[ext] = entry
-
 	if mimeType == "" {
 		defaultMutex.RLock()
 		mimeType = defaultMIME
 		defaultMutex.RUnlock()
 	}
 
+	// 插入新条目
+	entry := &mimeCacheEntry{ext: ext, mimeType: mimeType}
+	entry.element = mimeLRU.PushFront(entry)
+	mimeCache[ext] = entry
+
 	return mimeType
 }

internal/variable/builtin.go

@@ -255,7 +255,7 @@ func init() {
 		Name:        VarTimeLocal,
 		Description: "本地时间（格式：02/Jan/2024:15:04:05 +0800）",
 		Getter: func(_ *fasthttp.RequestCtx) string {
-			return time.Now().Format("02/Jan/2006:15:04:05 +0800")
+			return time.Now().Format("02/Jan/2006:15:04:05 -0700")
 		},
 	})
 
@@ -273,13 +273,15 @@ func init() {
 		Name:        VarRequestID,
 		Description: "唯一请求标识符",
 		Getter: func(ctx *fasthttp.RequestCtx) string {
-			// 先从 UserValue 获取，如果没有则生成
+			// 先从 UserValue 获取，如果没有则生成并缓存
 			if v := ctx.UserValue(VarRequestID); v != nil {
 				if s, ok := v.(string); ok {
 					return s
 				}
 			}
-			return uuid.New().String()
+			id := uuid.New().String()
+			ctx.SetUserValue(VarRequestID, id)
+			return id
 		},
 	})
 }

internal/variable/variable.go

@@ -117,7 +117,12 @@ func NewContext(ctx *fasthttp.RequestCtx) *Context {
 	vc, ok := pool.Get().(*Context)
 	if !ok {
 		// 池中类型不正确时返回新 Context
-		return &Context{ctx: ctx}
+		return &Context{
+			ctx:        ctx,
+			store:      make(map[string]string),
+			cache:      make(map[string]string),
+			bytesCache: make(map[string][]byte),
+		}
 	}
 	vc.ctx = ctx
 	vc.status = 0