wait doesn't seem to work on macOS. With an image file opened in Preview, the Promise fulfills only when the app is quit using Cmd+Q, and not when the window with the image is closed.

To reproduce:

opn("image.png").then(() => {
  // Won't run until Preview.app is quit with Cmd+Q
  console.log("Image viewer closed.")
}

I'm running opn on Electron.