Package trayhost is a cross-platform Go library to place an icon in the host operating system's taskbar.

• macOS - Fully implemented and supported by @dmitshur.
• Linux - Partially implemented, but unsupported (needs an owner/maintainer).
• Windows - Partially implemented, but unsupported (needs an owner/maintainer).

On macOS, for Notification Center user notifications to work, your Go binary that uses trayhost must be a part of a standard macOS app bundle.

Most other functionality of trayhost will be available if the binary is not a part of app bundle, but you will get a terminal pop up, and you will not be able to configure some aspects of the app.

Here's a minimal layout of an app bundle:

$ tree "Trayhost Example.app"
Trayhost\ Example.app
└── Contents
    ├── Info.plist
    ├── MacOS
    │   └── example
    └── Resources
        └── Icon.icns

Here's a minimal Info.plist file as reference (only the entries that are needed, nothing extra):

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "https://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>CFBundleExecutable</key>
	<string>example</string>
	<key>CFBundleIconFile</key>
	<string>Icon</string>
	<key>CFBundleIdentifier</key>
	<string>ExampleApp</string>
	<key>NSHighResolutionCapable</key>
	<true/>
	<key>LSUIElement</key>
	<string>1</string>
</dict>
</plist>

• CFBundleIdentifier needs to be set to some value for Notification Center to work.
• The binary must be inside Contents/MacOS directory for Notification Center to work.
• NSHighResolutionCapable to enable Retina mode.
• LSUIElement is needed to make the app not appear in Cmd+Tab list and the dock while still being able to show a tooltip in the menu bar.

On macOS, when you run an app bundle, the working directory of the executed process is the root directory (/), not the app bundle's Contents/Resources directory. Change directory to Resources if you need to load resources from there.

ep, err := os.Executable()
if err != nil {
	log.Fatalln("os.Executable:", err)
}
err = os.Chdir(filepath.Join(filepath.Dir(ep), "..", "Resources"))
if err != nil {
	log.Fatalln("os.Chdir:", err)
}

go get github.com/shurcooL/trayhost

• MIT License