dnstap.TapperFromContext always returns nil (#2018)

Automatically submitted.

plugin/dnstap/context_test.go

+package dnstap
+
+import (
+	"context"
+	"testing"
+)
+
+func TestDnstapContext(t *testing.T) {
+	ctx := tapContext{context.TODO(), Dnstap{}}
+	tapper := TapperFromContext(ctx)
+
+	if tapper == nil {
+		t.Fatal("Can't get tapper")
+	}
+}

plugin/dnstap/handler.go

@@ -51,7 +51,7 @@ func TapperFromContext(ctx context.Context) (t Tapper) {
 }
 
 // TapMessage implements Tapper.
-func (h *Dnstap) TapMessage(m *tap.Message) {
+func (h Dnstap) TapMessage(m *tap.Message) {
 	t := tap.Dnstap_MESSAGE
 	h.IO.Dnstap(tap.Dnstap{
 		Type:    &t,