This a full example of how PROT_EXEC works in mmap. More about it at https://brunocalza.me/2021/01/10/discovering-and-exploring-mmap-using-go/

mmap-exec.go

package main

import (
	"fmt"
	"unsafe"

	"github.com/edsrzf/mmap-go"
)

func main() {

	code := []byte{
		0x48, 0xc7, 0x44, 0x24, 0x10, 0x00, 0x00, 0x00, 0x00,
		0x48, 0x8b, 0x44, 0x24, 0x08,
		0x48, 0xff, 0xc0,
		0x48, 0x89, 0x44, 0x24, 0x10,
		0xc3,
	}

	memory, err := mmap.MapRegion(nil, len(code), mmap.EXEC|mmap.RDWR, mmap.ANON, 0)
	if err != nil {
		panic(err)
	}

	copy(memory, code)

	memory_ptr := &memory
	ptr := unsafe.Pointer(&memory_ptr)
	inc := *(*func(int) int)(ptr)

	fmt.Println(inc(10)) // Prints 11
}