You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: memory_windows.go
    path of file: ./repos/gotosocial/vendor/github.com/pbnjay/memory
    
    the code of the file until where you have to start completion: // +build windows

package mem
    
func sysFreeMemory() uint64 {
	kernel32, err := syscall.LoadDLL("kernel32.dll")
	if err != nil {
		return 0
	}
	// GetPhysicallyInstalledSystemMemory is simpler, but broken on
	// older versions of windows (and uses this under the hood anyway).
	globalMemoryStatusEx, err := kernel32.FindProc("GlobalMemoryStatusEx")
	if err != nil {
		return 0
	}
	msx := &memStatusEx{
		dwLength: 64,
	}
	r, _, _ := globalMemoryStatusEx.Call(uintptr(unsafe.Pointer(msx)))
	if r == 0 {
		return 0
	}
	return msx.ullAvailPhys
}