package main

import (
    "fmt"
    "bufio"
    "os"
    "unicode/utf8"
)

func main() {
    scanner := bufio.NewScanner(os.Stdin)
    for scanner.Scan() {
        s := scanner.Text()
        fmt.Println("Length: ",
            utf8.RuneCountInString(s),
            " Bytes: ",
            len(s))
    }
}

Built-in function len() shows number of bytes in string. For one-byte characters, such as ASCII, number of bytes in string and its length are the same value. But for multi-byte characters (Chinese, Russian and so on) these are two different values. Localized strings use more memory, than there are characters in them. That’s why to find a number of characters in a string the function RuneCountInString from package “unicode/utf8” should be used.

Another way to obtain numer of characters in a string is to cast the string to []rune and use len() built-in:

fmt.Println(len([]rune(s)))