How to set window position and make it unresizable in Go walk

I am trying to figure out the basics of working with the Go GUI library, walk.

For starters, I would like to be able to

1. Control the window's position
   hopefully in a way similar to what other languages provide (center on screen, center to parent, exact coordinates etc).
2. Make the window unresizable

This is the code I have, I was hoping the MaxSize declaration would solve the second problem, but it doesn't, and I was looking for some sort of a Position declaration but couldn't find anything that makes sense to me.

package main

import (
	// "github.com/lxn/walk"
	. "github.com/lxn/walk/declarative"
)

func main() {
	MainWindow{
		Title:   "Test",
		MinSize: Size{300, 50},
		MaxSize: Size{300, 50}, // Doesn't work
		// Position: ...        // Doesn't exist
		Layout: VBox{},
		Children: []Widget{
			Label{Text: "Hello World"},
		},
	}.Run()
}

It looks like walk doesn't provide this functionality in its own API. However, walk created on top of win which actually is just a Go bindings to WinAPI. So you can easily call any WinAPI functions. For example, to show a main window on a specified position one can call SetWindowPos():

package main

import (
	"github.com/lxn/win"
	"github.com/lxn/walk"
	. "github.com/lxn/walk/declarative"
)

const (
	SIZE_W = 600
	SIZE_H = 400
)

type MyMainWindow struct {
	*walk.MainWindow
}

func main() {
	mw := new(MyMainWindow)

	MainWindow{
		Visible: false,
		AssignTo: &mw.MainWindow,
	}.Create()

	defaultStyle := win.GetWindowLong(mw.Handle(), win.GWL_STYLE) // Gets current style
	newStyle := defaultStyle &^ win.WS_THICKFRAME                 // Remove WS_THICKFRAME
	win.SetWindowLong(mw.Handle(), win.GWL_STYLE, newStyle)

	xScreen := win.GetSystemMetrics(win.SM_CXSCREEN);
	yScreen := win.GetSystemMetrics(win.SM_CYSCREEN);
	win.SetWindowPos(
		mw.Handle(),
		0,
		(xScreen - SIZE_W)/2,
		(yScreen - SIZE_H)/2,
		SIZE_W,
		SIZE_H,
		win.SWP_FRAMECHANGED,
	)
	win.ShowWindow(mw.Handle(), win.SW_SHOW);

	mw.Run()
}

To make window unresizable you need to unset WS_THICKFRAME style, as shown in the example. More information can be found here.