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>

test/proxy_test.go

@@ -70,8 +70,7 @@ func BenchmarkProxyLookup(b *testing.B) {
 	m := new(dns.Msg)
 	m.SetQuestion("example.org.", dns.TypeA)
 
-	b.ResetTimer()
-	for range b.N {
+	for b.Loop() {
 		if _, err := dns.Exchange(m, udp); err != nil {
 			b.Fatal("Expected to receive reply, but didn't")
 		}