Go语言中byterune实质上就是uint8int32类型。byte用来强调数据是raw data,而不是数字;而rune用来表示Unicodecode point参考规范

uint8       the set of all unsigned  8-bit integers (0 to 255)
int32       the set of all signed 32-bit integers (-2147483648 to 2147483647)

byte        alias for uint8
rune        alias for int32

可以通过下面程序验证:

package main

import "fmt"

func byteSlice(b []byte) []byte {
    return b
}

func runeSlice(r []rune) []rune {
    return r
}

func main() {
    b := []byte{0, 1}
    u8 := []uint8{2, 3}
    fmt.Printf("%T %T \n", b, u8)
    fmt.Println(byteSlice(b))
    fmt.Println(byteSlice(u8))

    r := []rune{4, 5}
    i32 := []int32{6, 7}
    fmt.Printf("%T %T \n", r, i32)
    fmt.Println(runeSlice(r))
    fmt.Println(runeSlice(i32))
}

执行结果如下:

[]uint8 []uint8
[0 1]
[2 3]
[]int32 []int32
[4 5]
[6 7]

参考资料:
Difference between []uint8 && []byte (Golang Slices)