How to write a dynamic link library file？

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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?