change value of a private field in Go struct

change_val.go

package main

import (
	"fmt"
	"reflect"
	"unsafe"
)

type private struct {
	val string
}

func (p *private) Val() string {
	return p.val
}

type T interface {
	Val() string
}

func New() T {
	return &private{}
}

func changeVal[V any, P *V](dst any, name string, nval V) {
	dstRv := reflect.Indirect(reflect.ValueOf(dst))
	member := dstRv.FieldByName(name)
	ptrOfMember := unsafe.Pointer(member.UnsafeAddr())
	realPtrToY := (P)(ptrOfMember)
	*realPtrToY = nval
}

func main() {
	t := New()
	changeVal[string, *string](t, "val", "string")
	fmt.Println(t.Val())
}