Go range http://devs.cloudimmunity.com/gotchas-and-common-mistakes-in-go-golang/index.html

main.go

package main

import (
	"fmt"
)

func main() {
	data := "A\xfe\x02\xff\x04"
	for _, v := range data {
		fmt.Printf("%#x ", v) //0x41 0xfffd 0x2 0xfffd 0x4
	}

	fmt.Println()

	for _, v := range []byte(data) {
		fmt.Printf("%#x ", v) //0x41 0xfe 0x2 0xff 0x4
	}
}