I have made some experiments, in the 'darwin_ios.m' file, we can see the swapBuffers method:

void swapBuffers(GLintptr context) {
	__block EAGLContext* ctx = (EAGLContext*)context;
	dispatch_sync(dispatch_get_main_queue(), ^{
		[EAGLContext setCurrentContext:ctx];
		[ctx presentRenderbuffer:GL_RENDERBUFFER];
	});
}

If the App just resumed from the background, we can call [glview display] manually to restore GLKView' state, then very thing works well. There must be some code in the method, like bind framebuffer/renderbuffer... But gomobile didn't do these in the swapBuffers method.

But call [glview display] manually will has some unpredictable behavior, some times the app will just cash. In the old implementation, gomobile use ViewController's update loop:

- (void)update {
	drawgl((GoUintptr)self.context);
}

But in the current implementation, it use a custom for loop:

func (a *app) loop(ctx C.GLintptr) {
	runtime.LockOSThread()
	C.makeCurrentContext(ctx)

	workAvailable := a.worker.WorkAvailable()

	for {
		select {
		case <-workAvailable:
			a.worker.DoWork()
		case <-theApp.publish:
		loop1:
			for {
				select {
				case <-workAvailable:
					a.worker.DoWork()
				default:
					break loop1
				}
			}
			C.swapBuffers(ctx)
			theApp.publishResult <- PublishResult{}
		}
	}
}

And in cocos2dx, they use the CADisplayLink's loop(Apple best practice). So, is there any special reasons to use custom loop, and is there any quick way to fix this bug? @eliasnaur @crawshaw

Has anyone made progress on this?
I took the suggestion of @ntop001 but by calling [glview display] I found that more often than not the restoring app would crash.
Of course after that it comes back to life so perversely it's a small improvement over the frozen option...

@andydotxyz You can see my fixes here: KorokEngine/mobile@744fe39 . I have test it on Mac/PC/Android/iOS, it works well.

Oh you're a life saver. I hope you don't mind but I cherry-picked your fixes on top of the latest golang.org/x/mobile along with my own compile fixes - that's all at fyne-io/mobile, check it out if you like.

Change https://golang.org/cl/350211 mentions this issue: app: use system render loop on iOS