golang emoji中文字符串的截取

package main

import (
   "fmt"
   "unicode/utf8"
)

func main()  {
   str:="?表情"
   fmt.Println(utf8.RuneCountInString(str))
   fmt.Println(len(str))
   slice:=str[0:10]
   fmt.Println(slice)
   nameRune := []rune(str)
   fmt.Println(len(nameRune))
   fmt.Println("string = ",string(nameRune[0:len(nameRune)]))
}

output:

3
10
?表情
3
string =  ?表情