add logger wrapper (#715)

* add logger wrapper

log/log.go

@@ -1,8 +1,10 @@
 package log
 
+import "os"
+
 var (
 	// DefaultLogger is default logger.
-	DefaultLogger Logger = NewStdLogger()
+	DefaultLogger Logger = NewStdLogger(os.Stderr)
 )
 
 // Logger is a logger interface.

log/log_test.go

@@ -5,7 +5,7 @@ import (
 )
 
 func TestLogger(t *testing.T) {
-	logger := NewStdLogger()
+	logger := DefaultLogger
 	Debug(logger).Print("log", "test debug")
 	Info(logger).Print("log", "test info")
 	Warn(logger).Print("log", "test warn")

log/std.go

@@ -3,8 +3,8 @@ package log
 import (
 	"bytes"
 	"fmt"
+	"io"
 	"log"
-	"os"
 	"sync"
 )
 
@@ -16,9 +16,9 @@ type stdLogger struct {
 }
 
 // NewStdLogger new a std logger with options.
-func NewStdLogger() Logger {
+func NewStdLogger(w io.Writer) Logger {
 	return &stdLogger{
-		log: log.New(os.Stderr, "", log.LstdFlags),
+		log: log.New(w, "", log.LstdFlags),
 		pool: &sync.Pool{
 			New: func() interface{} {
 				return new(bytes.Buffer)

log/std_test.go

@@ -3,7 +3,7 @@ package log
 import "testing"
 
 func TestFmtLogger(t *testing.T) {
-	logger := NewStdLogger()
+	logger := DefaultLogger
 
 	Debug(logger).Print("log", "test debug")
 	Info(logger).Print("log", "test info")

log/wrapper.go

@@ -0,0 +1,14 @@
+package log
+
+type wrapper []Logger
+
+func (w wrapper) Print(pairs ...interface{}) {
+	for _, p := range w {
+		p.Print(pairs...)
+	}
+}
+
+// Wrap wraps multi logger.
+func Wrap(l ...Logger) Logger {
+	return wrapper(l)
+}

log/wrapper_test.go

@@ -0,0 +1,14 @@
+package log
+
+import (
+	"os"
+	"testing"
+)
+
+func TestWrapper(t *testing.T) {
+	out := NewStdLogger(os.Stdout)
+	err := NewStdLogger(os.Stderr)
+
+	l := Wrap(out, err)
+	l.Print("message", "test")
+}