feat: use writer directly in stdLogger. (#3121)

* feat: use writer directly in stdLogger.

* fix: Add newlines for each Log

* fix: remove break changes.

---------

Co-authored-by: Daemon <haiyux@foxmail.com>

log/std.go

@@ -4,21 +4,25 @@ import (
 	"bytes"
 	"fmt"
 	"io"
-	"log"
 	"sync"
 )
 
 var _ Logger = (*stdLogger)(nil)
 
+// stdLogger corresponds to the standard library's [log.Logger] and provides
+// similar capabilities. It also can be used concurrently by multiple goroutines.
 type stdLogger struct {
-	log  *log.Logger
-	pool *sync.Pool
+	w         io.Writer
+	isDiscard bool
+	mu        sync.Mutex
+	pool      *sync.Pool
 }
 
 // NewStdLogger new a logger with writer.
 func NewStdLogger(w io.Writer) Logger {
 	return &stdLogger{
-		log: log.New(w, "", 0),
+		w:         w,
+		isDiscard: w == io.Discard,
 		pool: &sync.Pool{
 			New: func() interface{} {
 				return new(bytes.Buffer)
@@ -29,21 +33,27 @@ func NewStdLogger(w io.Writer) Logger {
 
 // Log print the kv pairs log.
 func (l *stdLogger) Log(level Level, keyvals ...interface{}) error {
-	if len(keyvals) == 0 {
+	if l.isDiscard || len(keyvals) == 0 {
 		return nil
 	}
 	if (len(keyvals) & 1) == 1 {
 		keyvals = append(keyvals, "KEYVALS UNPAIRED")
 	}
+
 	buf := l.pool.Get().(*bytes.Buffer)
+	defer l.pool.Put(buf)
+
 	buf.WriteString(level.String())
 	for i := 0; i < len(keyvals); i += 2 {
 		_, _ = fmt.Fprintf(buf, " %s=%v", keyvals[i], keyvals[i+1])
 	}
-	_ = l.log.Output(4, buf.String()) //nolint:gomnd
-	buf.Reset()
-	l.pool.Put(buf)
-	return nil
+	buf.WriteByte('\n')
+	defer buf.Reset()
+
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	_, err := l.w.Write(buf.Bytes())
+	return err
 }
 
 func (l *stdLogger) Close() error {

log/std_test.go

@@ -1,6 +1,11 @@
 package log
 
-import "testing"
+import (
+	"bytes"
+	"testing"
+
+	"golang.org/x/sync/errgroup"
+)
 
 func TestStdLogger(_ *testing.T) {
 	logger := DefaultLogger
@@ -15,3 +20,21 @@ func TestStdLogger(_ *testing.T) {
 	logger2 := DefaultLogger
 	_ = logger2.Log(LevelDebug)
 }
+
+func TestStdLogger_Log(t *testing.T) {
+	var b bytes.Buffer
+	logger := NewStdLogger(&b)
+
+	var eg errgroup.Group
+	eg.Go(func() error { return logger.Log(LevelInfo, "msg", "a", "k", "v") })
+	eg.Go(func() error { return logger.Log(LevelInfo, "msg", "a", "k", "v") })
+
+	err := eg.Wait()
+	if err != nil {
+		t.Fatalf("log error: %v", err)
+	}
+
+	if s := b.String(); s != "INFO msg=a k=v\nINFO msg=a k=v\n" {
+		t.Fatalf("log not match: %q", s)
+	}
+}