How to write a dynamic link library file？

[nowayout]

I am preparing to write a dynamic link library file，it contains a winform. The code such as:

`
func init() {
title := "Spark"
hInst := win.GetModuleHandle(nil)
if hInst == 0 {
panic(fmt.Sprintf("GetModuleHandle: %v", win.GetLastError()))
}

wc := win.WNDCLASSEX{}
wc.CbSize = uint32(unsafe.Sizeof(wc))
wc.LpfnWndProc = syscall.NewCallback(wndProc)
wc.HInstance = hInst
wc.HbrBackground = win.COLOR_WINDOW + 1
wc.LpszClassName = syscall.StringToUTF16Ptr(title)
wc.Style = win.CS_HREDRAW | win.CS_VREDRAW
if atom := win.RegisterClassEx(&wc); atom == 0 {
	panic(fmt.Sprintf("RegisterClassEx: %v", win.GetLastError()))
}

hwnd = win.CreateWindowEx(
	win.WS_EX_TOOLWINDOW,
	syscall.StringToUTF16Ptr(title),
	syscall.StringToUTF16Ptr(title),
	win.WS_VISIBLE | win.WS_POPUP,
	0,
	0,
	0,
	0,
	0,
	0,
	hInst,
	nil,
)
if hwnd == 0 {
	panic(fmt.Sprintf("CreateWindowEx: %v", win.GetLastError()))
}

win.ShowWindow(hwnd, win.SW_HIDE)
win.UpdateWindow(hwnd)

var msg win.MSG
for {
	if m := win.GetMessage(&msg, 0, 0, 0); m != 0 {
		win.TranslateMessage(&msg)
		win.DispatchMessage(&msg)
	}
}

}

func wndProc(hwnd win.HWND, msg uint32, wparam, lparam uintptr) (result uintptr) {
switch msg {
case win.WM_DESTROY:
win.PostQuitMessage(0)
case win.WM_DEVICECHANGE:
OnDeviceChange(hwnd, msg, wparam, lparam)
case WM_USB_EVENT: // Customer Message
OnUsbEvent(hwnd, msg, wparam, lparam)
default:
return win.DefWindowProc(hwnd, msg, wparam, lparam)
}
return 0
}

//export DoPausePlay
func DoPausePlay() *C.char {
doPause()

return C.CString("0")

}
`

But when another program calls, it hangs at this code:

for { if m := win.GetMessage(&msg, 0, 0, 0); m != 0 { win.TranslateMessage(&msg) win.DispatchMessage(&msg) } }
Other methods, such as DoPausePlay(), cannot be called. How can I change this?