log instead of fmt

plugin/dnstap/dnstapio/io.go

@@ -1,17 +1,20 @@
 package dnstapio
 
 import (
-	"fmt"
 	"io"
+	"log"
 	"os"
 
 	tap "github.com/dnstap/golang-dnstap"
 	"github.com/golang/protobuf/proto"
 )
 
+func init() {
+	log.SetOutput(os.Stdout)
+}
+
 // DnstapIO wraps the dnstap I/O routine.
 type DnstapIO struct {
-	iolog  io.Writer
 	writer io.WriteCloser
 	queue  chan tap.Dnstap
 	stop   chan bool
@@ -27,7 +30,7 @@ type Protocol interface {
 
 // New dnstap I/O routine from Protocol.
 func New(w Protocol) *DnstapIO {
-	dio := DnstapIO{iolog: os.Stdout}
+	dio := DnstapIO{}
 	dio.writer = w
 	dio.queue = make(chan tap.Dnstap, 10)
 	dio.stop = make(chan bool)
@@ -40,7 +43,7 @@ func (dio *DnstapIO) Dnstap(payload tap.Dnstap) {
 	select {
 	case dio.queue <- payload:
 	default:
-		fmt.Fprintln(dio.iolog, "[WARN] Dnstap payload dropped.")
+		log.Println("[WARN] Dnstap payload dropped.")
 	}
 }
 
@@ -52,7 +55,7 @@ func (dio *DnstapIO) serve() {
 			if err == nil {
 				dio.writer.Write(frame)
 			} else {
-				fmt.Fprintf(dio.iolog, "[ERROR] Invalid dnstap payload dropped: %s\n", err)
+				log.Printf("[ERROR] Invalid dnstap payload dropped: %s\n", err)
 			}
 		case <-dio.stop:
 			close(dio.queue)

plugin/dnstap/dnstapio/io_test.go

@@ -3,6 +3,7 @@ package dnstapio
 import (
 	"bytes"
 	"io/ioutil"
+	"log"
 	"sync"
 	"testing"
 	"time"
@@ -10,6 +11,10 @@ import (
 	tap "github.com/dnstap/golang-dnstap"
 )
 
+func init() {
+	log.SetOutput(ioutil.Discard)
+}
+
 type buf struct {
 	*bytes.Buffer
 	cost time.Duration
@@ -27,7 +32,6 @@ func (b buf) Close() error {
 func TestRace(t *testing.T) {
 	b := buf{&bytes.Buffer{}, 100 * time.Millisecond}
 	dio := New(b)
-	dio.iolog = ioutil.Discard // don't flood Travis
 	wg := &sync.WaitGroup{}
 	wg.Add(10)
 	for i := 0; i < 10; i++ {