Remove extra nil

Signed-off-by: Antoine Tenart <antoine.tenart@ack.tf>

main.go

@@ -41,7 +41,7 @@ func main() {
 	fmt.Print(generateList())
 }
 
-func generateList() (string, error) {
+func generateList() string {
 	c := make(chan string)
 	for _, list := range lists {
 		go handle(list, c)
@@ -52,7 +52,7 @@ func generateList() (string, error) {
 		zones = append(zones, <-c)
 	}
 
-	return strings.Join(zones, "\n"), nil
+	return strings.Join(zones, "\n")
 }
 
 func handle(url string, zone chan string) {