feat(log): Add writer for log (#138)

Signed-off-by: Flc゛ <four_leaf_clover@foxmail.com>

log/writer/writer.go

@@ -0,0 +1,23 @@
+package writer
+
+import (
+	"io"
+
+	"github.com/go-kratos/kratos/v2/log"
+)
+
+type Writer struct {
+	logger log.Logger
+}
+
+var _ io.Writer = (*Writer)(nil)
+
+func New(logger log.Logger) *Writer {
+	return &Writer{
+		logger: logger,
+	}
+}
+
+func (w *Writer) Write(p []byte) (n int, err error) {
+	return len(p), w.logger.Log(log.LevelInfo, string(p))
+}

log/writer/writer_test.go

@@ -0,0 +1,37 @@
+package writer
+
+import (
+	"testing"
+
+	"github.com/go-kratos/kratos/v2/log"
+	"github.com/stretchr/testify/assert"
+)
+
+var result = make(chan data, 1)
+
+type data struct {
+	level   log.Level
+	keyvals []interface{}
+}
+
+type logger struct{}
+
+func (l *logger) Log(level log.Level, keyvals ...interface{}) error {
+	result <- data{
+		level:   level,
+		keyvals: keyvals,
+	}
+	return nil
+}
+
+func TestWriter(t *testing.T) {
+	w := New(&logger{})
+
+	n, err := w.Write([]byte("test"))
+	assert.NoError(t, err)
+	assert.Equal(t, 4, n)
+
+	d := <-result
+	assert.Equal(t, log.LevelInfo, d.level)
+	assert.Equal(t, "test", d.keyvals[0])
+}