diff --git a/aof.go b/aof.go
index d410a86..6dfa4ad 100644
--- a/aof.go
+++ b/aof.go
@@ -5,7 +5,6 @@ import (
 	"github.com/hdt3213/godis/datastruct/dict"
 	"github.com/hdt3213/godis/datastruct/lock"
 	"github.com/hdt3213/godis/lib/logger"
-	"github.com/hdt3213/godis/lib/utils"
 	"github.com/hdt3213/godis/redis/parser"
 	"github.com/hdt3213/godis/redis/reply"
 	"io"
@@ -78,7 +77,12 @@ func (db *DB) loadAof(maxBytes int) {
 	}
 	defer file.Close()
 
-	reader := utils.NewLimitedReader(file, maxBytes)
+	var reader io.Reader
+	if maxBytes > 0 {
+		reader = io.LimitReader(file, int64(maxBytes))
+	} else {
+		reader = file
+	}
 	ch := parser.ParseStream(reader)
 	for p := range ch {
 		if p.Err != nil {
diff --git a/lib/logger/logger.go b/lib/logger/logger.go
index 2bfbfe9..ddacba5 100644
--- a/lib/logger/logger.go
+++ b/lib/logger/logger.go
@@ -7,6 +7,7 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
+	"sync"
 	"time"
 )
 
@@ -23,6 +24,7 @@ var (
 	defaultPrefix      = ""
 	defaultCallerDepth = 2
 	logger             *log.Logger
+	mu                 sync.Mutex
 	logPrefix          = ""
 	levelFlags         = []string{"DEBUG", "INFO", "WARN", "ERROR", "FATAL"}
 )
@@ -75,30 +77,40 @@ func setPrefix(level logLevel) {
 
 // Debug prints debug log
 func Debug(v ...interface{}) {
+	mu.Lock()
+	defer mu.Unlock()
 	setPrefix(DEBUG)
 	logger.Println(v...)
 }
 
 // Info prints normal log
 func Info(v ...interface{}) {
+	mu.Lock()
+	defer mu.Unlock()
 	setPrefix(INFO)
 	logger.Println(v...)
 }
 
 // Warn prints warning log
 func Warn(v ...interface{}) {
+	mu.Lock()
+	defer mu.Unlock()
 	setPrefix(WARNING)
 	logger.Println(v...)
 }
 
 // Error prints error log
 func Error(v ...interface{}) {
+	mu.Lock()
+	defer mu.Unlock()
 	setPrefix(ERROR)
 	logger.Println(v...)
 }
 
 // Fatal prints error log then stop the program
 func Fatal(v ...interface{}) {
+	mu.Lock()
+	defer mu.Unlock()
 	setPrefix(FATAL)
 	logger.Fatalln(v...)
 }
diff --git a/lib/utils/limited_reader.go b/lib/utils/limited_reader.go
deleted file mode 100644
index f02fa31..0000000
--- a/lib/utils/limited_reader.go
+++ /dev/null
@@ -1,37 +0,0 @@
-package utils
-
-import (
-	"errors"
-	"io"
-)
-
-// LimitedReader implements io.Reader, but you can only read the given number of bytes
-type LimitedReader struct {
-	src   io.Reader
-	n     int
-	limit int
-}
-
-// NewLimitedReader wraps an io.Reader to LimitedReader
-func NewLimitedReader(src io.Reader, limit int) *LimitedReader {
-	return &LimitedReader{
-		src:   src,
-		limit: limit,
-	}
-}
-
-// Read reads up to len(p) bytes into p. if meets EOF from src or reach limit, it returns EOF
-func (r *LimitedReader) Read(p []byte) (n int, err error) {
-	if r.src == nil {
-		return 0, errors.New("no data source")
-	}
-	if r.limit > 0 && r.n >= r.limit {
-		return 0, io.EOF
-	}
-	n, err = r.src.Read(p)
-	if err != nil {
-		return n, err
-	}
-	r.n += n
-	return
-}