kind of working finally

internal/xhotkey/mainthread/doc.go

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+// Copyright 2022 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+// Package mainthread wrapps the golang.design/x/mainthread, and
+// provides a different implementation for macOS so that it can
+// handle main thread events for the NSApplication.
+package mainthread

internal/xhotkey/mainthread/os.go

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+// Copyright 2022 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+//go:build windows || linux || (darwin && !cgo)
+
+package mainthread
+
+import "golang.design/x/mainthread"
+
+// Call calls f on the main thread and blocks until f finishes.
+func Call(f func()) { mainthread.Call(f) }
+
+// Init initializes the functionality of running arbitrary subsequent functions be called on the main system thread.
+//
+// Init must be called in the main.main function.
+func Init(main func()) { mainthread.Init(main) }

internal/xhotkey/mainthread/os_darwin.go

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+// Copyright 2022 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+//go:build darwin
+
+package mainthread
+
+/*
+#cgo CFLAGS: -x objective-c
+#cgo LDFLAGS: -framework Cocoa
+#import <Cocoa/Cocoa.h>
+#import <Dispatch/Dispatch.h>
+
+extern void os_main(void);
+extern void wakeupMainThread(void);
+static bool isMainThread() {
+	return [NSThread isMainThread];
+}
+*/
+import "C"
+import (
+	"os"
+	"runtime"
+)
+
+func init() {
+	runtime.LockOSThread()
+}
+
+// Call calls f on the main thread and blocks until f finishes.
+func Call(f func()) {
+	if C.isMainThread() {
+		f()
+		return
+	}
+	go func() {
+		mainFuncs <- f
+		C.wakeupMainThread()
+	}()
+}
+
+// Init initializes the functionality of running arbitrary subsequent functions be called on the main system thread.
+//
+// Init must be called in the main.main function.
+func Init(f func()) {
+	go func() {
+		f()
+		os.Exit(0)
+	}()
+
+	C.os_main()
+}
+
+var mainFuncs = make(chan func(), 1)
+
+//export dispatchMainFuncs
+func dispatchMainFuncs() {
+	for {
+		select {
+		case f := <-mainFuncs:
+			f()
+		default:
+			return
+		}
+	}
+}

internal/xhotkey/mainthread/os_darwin.m

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+// Copyright 2022 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+//go:build darwin
+
+#include <stdint.h>
+#import <Cocoa/Cocoa.h>
+
+extern void dispatchMainFuncs();
+
+void wakeupMainThread(void) {
+	dispatch_async(dispatch_get_main_queue(), ^{
+		dispatchMainFuncs();
+	});
+}
+
+// The following three lines of code must run on the main thread.
+// It must handle it using golang.design/x/mainthread.
+//
+// inspired from here: https://github.com/cehoffman/dotfiles/blob/4be8e893517e970d40746a9bdc67fe5832dd1c33/os/mac/iTerm2HotKey.m
+void os_main(void) {
+	[NSApplication sharedApplication];
+	[NSApp disableRelaunchOnLogin];
+	[NSApp run];
+}