chore(lint): modernize Go (#7536)

Use modern Go constructs through the modernize analyzer from the
golang.org/x/tools package.

Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>

plugin/file/lookup_test.go

@@ -316,9 +316,7 @@ func BenchmarkFileLookup(b *testing.B) {
 
 	m := tc.Msg()
 
-	b.ResetTimer()
-
-	for range b.N {
+	for b.Loop() {
 		fm.ServeDNS(ctx, rec, m)
 	}
 }