partial fix for mac

internal/sdl/sdl.go

@@ -49,6 +49,8 @@ var (
 	sdlCreateWindow  func(title *byte, w, h int32, flags uint64) uintptr
 	sdlDestroyWindow func(window uintptr)
 
+	sdlVulkanLoadLibrary           func(path *byte) bool
+	sdlVulkanUnloadLibrary         func()
 	sdlVulkanGetInstanceExtensions func(count *uint32) uintptr
 	sdlVulkanCreateSurface         func(window, instance, allocator uintptr, surface *uint64) bool
 
@@ -153,8 +155,13 @@ func Load() error {
 	purego.RegisterLibFunc(&sdlGetError, h, "SDL_GetError")
 	purego.RegisterLibFunc(&sdlCreateWindow, h, "SDL_CreateWindow")
 	purego.RegisterLibFunc(&sdlDestroyWindow, h, "SDL_DestroyWindow")
+
+	// vulkan
+	purego.RegisterLibFunc(&sdlVulkanLoadLibrary, h, "SDL_Vulkan_LoadLibrary")
+	purego.RegisterLibFunc(&sdlVulkanUnloadLibrary, h, "SDL_Vulkan_UnloadLibrary")
 	purego.RegisterLibFunc(&sdlVulkanGetInstanceExtensions, h, "SDL_Vulkan_GetInstanceExtensions")
 	purego.RegisterLibFunc(&sdlVulkanCreateSurface, h, "SDL_Vulkan_CreateSurface")
+
 	purego.RegisterLibFunc(&sdlPollEvent, h, "SDL_PollEvent")
 	purego.RegisterLibFunc(&sdlGetWindowSizeInPixels, h, "SDL_GetWindowSizeInPixels")
 	purego.RegisterLibFunc(&sdlSetWindowFullscreen, h, "SDL_SetWindowFullscreen")
@@ -186,6 +193,14 @@ func CreateWindow(title string, w, h int32, flags uint64) uintptr {
 }
 func DestroyWindow(window uintptr) { sdlDestroyWindow(window) }
 
+func VulkanLoadLibrary(path string) bool {
+	return sdlVulkanLoadLibrary(cbytes(path))
+}
+
+func VulkanUnloadLibrary() {
+	sdlVulkanUnloadLibrary()
+}
+
 func VulkanGetInstanceExtensions() []string {
 	var count uint32
 	vkExts := sdlVulkanGetInstanceExtensions(&count)