lint: enable intrange linter (#7331)

Enable intrange linter to enforce modern Go range syntax over
traditional for loops, by converting:

for i := 0; i < n; i++

to:

for i := range n

Adding type conversions where needed for compatibility
with existing uint64 parameters.

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

plugin/clouddns/clouddns.go

@@ -211,7 +211,7 @@ func (h *CloudDNS) updateZones(ctx context.Context) error {
 	// Collect errors (if any). This will also sync on all zones updates
 	// completion.
 	var errs []string
-	for i := 0; i < len(h.zones); i++ {
+	for range len(h.zones) {
 		err := <-errc
 		if err != nil {
 			errs = append(errs, err.Error())

plugin/clouddns/setup.go

@@ -43,7 +43,7 @@ func setup(c *caddy.Controller) error {
 
 		args := c.RemainingArgs()
 
-		for i := 0; i < len(args); i++ {
+		for i := range args {
 			parts := strings.SplitN(args[i], ":", 3)
 			if len(parts) != 3 {
 				return plugin.Error("clouddns", c.Errf("invalid zone %q", args[i]))