Parsing Perl regex with golang - regex

Question

http://play.golang.org/p/GM0SWo0qGs
This is my code and playground.
func insert_comma(input_num int) string {
temp_str := strconv.Itoa(input_num)
var validID = regexp.MustCompile(`\B(?=(\d{3})+$)`)
return validID.ReplaceAllString(temp_str, ",")
}
func main() {
fmt.Println(insert_comma(1000000000))
}
Basically, my desired input is 1,000,000,000.
And the regular expression works in Javascript but I do not know how to make this Perl regex work in Go. I would greatly appreciate it. Thanks,

Answer 1

Since lookahead assertion seems to be not supported, I'm providing you a different algorithm with no regexp:
Perl code:
sub insert_comma {
my $x=shift;
my $l=length($x);
for (my $i=$l%3==0?3:$l%3;$i<$l;$i+=3) {
substr($x,$i++,0)=',';
}
return $x;
}
print insert_comma(1000000000);
Go code: Disclaimer: I have zero experience with Go, so bear with me if I have errors and feel free to edit my post!
func insert_comma(input_num int) string {
temp_str := strconv.Itoa(input_num)
var result []string
i := len(temp_str)%3;
if i == 0 { i = 3 }
for index,element := range strings.Split(temp_str, "") {
if i == index {
result = append(result, ",");
i += 3;
}
result = append(result, element)
}
return strings.Join(result, "")
}
func main() {
fmt.Println(insert_comma(1000000000))
}
http://play.golang.org/p/7pvo7-3G-s