log instead of fmt

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++ {