How to count the number of consecutively repeated characters in a string

Basically, what I want to achieve is to not allow passwords with lots of consecutively repeated chars/digits.
I'm trying to write a <strong>go</strong> function to which I pass a string and a maximum allowed number of consecutively repeated characters, and it should tell me if it's surpassed or not.

I used to do it easily in <strong>javascript</strong> using the a regular expression in the following way:

var regexString = '(.)\{' + (maxAllowedRepetitions) + ',}';
var regex = new RegExp(regexString);
return regex.test(string)

... where maxAllowedRepetitions is the max limit. If the limit is 3 and a string is 'blablabla', it returns false. If it is blablaaaabla, it returns true since the character 'a' is repeated more than 3 times.

I'm finding it difficult to achieve the same thing using <strong>go</strong> regexp.
I don't mind not using regexp. I just need a good way to achieve this.
Any suggestions?

https://play.golang.org/p/HeK3f4uEvz

package main

import "fmt"

func main() {

	// invalid password with repetition
	password := "blablaaaabla"
	fmt.Printf("%s invalid ? %+v\n", password, invalid(password))

	// correct password with no repetition
	password = "blabla"
	fmt.Printf("%s invalid ? %+v\n", password, invalid(password))

	// valid password with unicode character
	password = "bla∞∞bla"
	fmt.Printf("%s invalid ? %+v\n", password, invalid(password))

	// invalid password with unicode character
	password = "bla∞∞∞bla"
	fmt.Printf("%s invalid ? %+v\n", password, invalid(password))
}

func invalid(s string) bool {
	var lastChar rune
	var lastCharCount = 0
	for _, c := range s {
		if c == lastChar {
			lastCharCount++
			if lastCharCount >= 3 {
				return true
			}
		} else {
			lastChar = c
			lastCharCount = 1
		}
	}

	return false
}

results

blablaaaabla invalid ? true
blabla invalid ? false
bla∞∞bla invalid ? false
bla∞∞∞bla invalid ? true

This works:

func AbideMaxRepetitions(max int, s string) bool {
	var rr rune
	rc := 0
	for _, r := range s {
		if rr == r {
			rc++
			if rc > max {
				return false
			}
		} else {
			rr = r
			rc = 1
		}

	}
	return true
}

When running:

func main() {
	ss := []string{"pass", "paaass", "paaaaaaaaaass", "ppa", "pppa", "x", "xx", "xxx"}
	for _, s := range ss {
		fmt.Printf("%q: %v\n", s, AbideMaxRepetitions(2, s))
	}
}

Prints:

"pass": true
"paaass": false
"paaaaaaaaaass": false
"ppa": true
"pppa": false
"x": true
"xx": true
"xxx": false

A simple loop should do the trick. Just remember that Go uses UTF8 for strings. You need to compare Runes (character) not bytes.