You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: sample_unicode.go
    path of file: ./repos/pmd/pmd-go/src/test/resources/net/sourceforge/pmd/lang/go/cpd/testdata
    
    the code of the file until where you have to start completion: func main() {
	//string底层是一个byte数组，因此string也可以进行切片操作
	str := "hello world"//string是不可变的
	slice := str[4:]

    
func main() {
	//string底层是一个byte数组，因此string也可以进行切片操作
	str := "hello world"//string是不可变的
	slice := str[4:]
	fmt.Println(slice)

	//若要对string进行修改需要将string修改为byte或rune的切片在操作
	//但是转为byte无法进行中文操作
	bytes := []byte(str)
	bytes[2] = 'x'
	str = string(bytes)
	fmt.Println(str)

	//转换成rune可以对中文进行操作
	runes := []rune(str)
	runes[0] = '哈'
	str = string(runes)
	fmt.Println(str)

}