gistfile1.go

package main

import (
    "io/ioutil"
    "unsafe"
)

type Data struct {
    Head [4]byte
    Flags byte
    Meta [2]byte
}

func main() {
    var data Data = Data{[4]byte{1, 2, 3, 4}, 5, [2]byte{6, 7}}

    obj := (*[7]byte)(unsafe.Pointer(&data))
    s := make([]byte, 10)
    s[0] = 1
    s[1] = 2
    s[2] = 3
    copy(s[3:], obj[:])
    ioutil.WriteFile("out.bin", s, 0666)
}