have a workaround to avoid crash on old macOS versions

README.md

@@ -62,7 +62,7 @@ Now look for *Awesome App* in your menu bar!
 
 ## The Webview example
 
-The code under `webview_example` is to demostrate how it can co-exist with other UI elements.
+The code under `webview_example` is to demostrate how it can co-exist with other UI elements. Note that the example doesn't work on macOS versions older than 10.15 Catalina.
 
 ## Platform notes
 

systray.go

@@ -78,6 +78,8 @@ func Run(onReady func(), onExit func()) {
 // Register initializes GUI and registers the callbacks but relies on the
 // caller to run the event loop somewhere else. It's useful if the program
 // needs to show other UI elements, for example, webview.
+// To overcome some OS weirdness, On macOS versions before Catalina, calling
+// this does exactly the same as Run().
 func Register(onReady func(), onExit func()) {
 	if onReady == nil {
 		systrayReady = func() {}

systray_darwin.m

@@ -212,10 +212,18 @@ NSMenuItem *find_menu_item(NSMenu *ourMenu, NSNumber *menuId) {
 void registerSystray(void) {
   AppDelegate *delegate = [[AppDelegate alloc] init];
   [[NSApplication sharedApplication] setDelegate:delegate];
+  // A workaround to avoid crashing on macOS versions before Catalina. Somehow
+  // SIGSEGV would happen inside AppKit if [NSApp run] is called from a
+  // different function, even if that function is called right after this.
+  if (floor(NSAppKitVersionNumber) <= /*NSAppKitVersionNumber10_14*/ 1671){
+    [NSApp run];
+  }
 }
 
 int nativeLoop(void) {
-  [NSApp run];
+  if (floor(NSAppKitVersionNumber) > /*NSAppKitVersionNumber10_14*/ 1671){
+    [NSApp run];
+  }
   return EXIT_SUCCESS;
 }