I'm developing a daemon with no UI apart from a simple icon in the Windows systray.

I would like to have no dependencies on any other package(s), so I'm trying to use the syscall package and implement the necessary call(s) by myself.

Documentation

• After some research, I think that I must use the Shell_NotifyIcon function in shell32.dll.
• The Golang WIKI gives three ways to call a Windows DLL. The third solution is to be excluded. For many reasons, I want to build sources with the Golang compiler only.
• I found an interesting article on "Developing for Multiple Platforms With Go" which explained how to use Shell_NotifyIconW (Unicode declination), but the implementation is partial.
• I have found a few Golang libraries which implement Windows System Tray. They are useful to help understand the structure and calls involved in dealing with it.

Libraries

• getlantern/systray
• cratonica/trayhost
• xilp/systray
• lxn/walk

Implementation

Structures

Built with xilp/systray documentation.

type HANDLE uintptr

type HICON HANDLE
    type HWND HANDLE

type GUID struct {
    Data1 uint32
    Data2 uint16
    Data3 uint16
    Data4 [8]byte
}

type NOTIFYICONDATA struct {
    CbSize           uint32
    HWnd             HWND
    UID              uint32
    UFlags           uint32
    UCallbackMessage uint32
    HIcon            HICON
    SzTip            [128]uint16
    DwState          uint32
    DwStateMask      uint32
    SzInfo           [256]uint16
    UVersion         uint32
    SzInfoTitle      [64]uint16
    DwInfoFlags      uint32
    GuidItem         GUID
}

Variables

const (
    NIM_ADD = 0x00000000
    NIM_MODIFY = 0x00000001
    NIM_DELETE = 0x00000002
    NIM_SETVERSION = 0x00000004

    NIF_MESSAGE = 0x00000001
    NIF_ICON = 0x00000002
    NIF_TIP = 0x00000004
    NIF_STATE = 0x00000008

    NIF_HIDDEN = 0x00000001
)

Source

package main

import (
    "log"
    "syscall"
    "unsafe"
)

func main() {
    shell32 := syscall.MustLoadDLL("shell32.dll")
    Shell_NotifyIcon := shell32.MustFindProc("Shell_NotifyIconW")

    iconData := NOTIFYICONDATA{
        HWnd: 0,
        UFlags: NIF_MESSAGE | NIF_STATE,
        DwState: NIF_HIDDEN,
        DwStateMask: NIS_HIDDEN,
    }
    iconData.CbSize = uint32(unsafe.Sizeof(iconData))

    ret, _, _ := Shell_NotifyIcon.Call(
        NIM_ADD,
        uintptr(unsafe.Pointer(&iconData)),
    )

    if ret == 0 {
        log.Println("Failed")
        return
    }

    // Do anything, like open a HTTP server to keep the program running
    http.ListenAndServe(":8080", nil)
}

Details

• I have no idea what information to give in HWnd, but without it, the executable crashes.
• UFlags, DwState and DwStateMask have values that I have found in different projects.

I know that it is possible; the Golang WIKI gives an implementation to call a message box.