Hostname (Single Label, RFC 1123)

const re = new RegExp("^[a-zA-Z0-9](?:[a-zA-Z0-9\\-]{0,61}[a-zA-Z0-9])?$", "");
const input = "web-01";
const match = input.match(re);
console.log(match ? match[0] : null);

import re

pattern = re.compile(r"^[a-zA-Z0-9](?:[a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?$")
input_text = "web-01"
for m in pattern.finditer(input_text):
    print(m.group(0))

package main

import (
	"fmt"
	"regexp"
)

func main() {
	re := regexp.MustCompile(`^[a-zA-Z0-9](?:[a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?$`)
	input := `web-01`
	for _, match := range re.FindAllString(input, -1) {
		fmt.Println(match)
	}
}