golang获取字符串长度需要注意的地方

package main

import (
    "fmt"
    "unicode/utf8"
)

func main() {
    aa := "猪头"
    bb := "12345"

    fmt.Println(utf8.RuneCountInString(aa),len(aa))
    fmt.Println(utf8.RuneCountInString(bb),len(bb))
}