Hammerspoon: Configure volume via keyboard shortcuts for macbook pro (touchbar, but no keys)

volume.lua

function changeVolume(diff)
  return function()
    local current = hs.audiodevice.defaultOutputDevice():volume()
    local new = math.min(100, math.max(0, math.floor(current + diff)))
    if new > 0 then
      hs.audiodevice.defaultOutputDevice():setMuted(false)
    end
    hs.alert.closeAll(0.0)
    hs.alert.show("Volume " .. new .. "%", {}, 0.5)
    hs.audiodevice.defaultOutputDevice():setVolume(new)
  end
end

hs.hotkey.bind({'ctrl', 'alt', 'cmd'}, 'Down', changeVolume(-3))
hs.hotkey.bind({'ctrl', 'alt', 'cmd'}, 'Up', changeVolume(3))

Thanks so much Alexander for getting back to me so quickly.
I am on same mac and hammerspoon versions. very new on lua, not sure how to display debug msg in lua.
The wired part is, if I have click volumn icon on menu bar, volumn list is displayed, your hotkey works properly.

But I am in other application, use the hotkey, will not affect volumn at all

Thanks so much

works perfectly on my mechine, macOS 13.3.1, Hammerspoon 0.9.100.