Signed and notarized Go app not launching after Gatekeeper dialog

As bogdansrc mentioned, Gatekeeper only applies to application bundles that have a com.apple.quarantine extended attribute. Some applications (like μTorrent) don't add them to the files they download, and some unarchiving programs (like unzip) don't add them to files after extracting archives.

You can list extended attributes with xattr -l.

Gatekeeper is also disabled if you have disabled LSQuarantine with for example defaults write com.apple.LaunchServices LSQuarantine -bool false.

You could create an Automator service with a Run Shell Script action like this:

for f; do
  q=$(xattr -p com.apple.quarantine "$f" 2> /dev/null)
  if [[ $q ]]; then
    xattr -d com.apple.quarantine "$f"
    open "$f"
    xattr -w com.apple.quarantine "$q" "$f"
  else
    open "$f"
  fi
done

Set the input type to files or folders (just folders doesn't seem to include application bundles) and set "pass input" to "as arguments".

Or in Alfred 2 you could add a File Action trigger and connect it to a Run Script action like this:

f="{query}"
q=$(xattr -p com.apple.quarantine "$f" 2> /dev/null)
if [[ $q ]]; then
  xattr -d com.apple.quarantine "$f"
  open "$f"
  xattr -w com.apple.quarantine "$q" "$f"
else
  open "$f"
fi

If you want to keep Gatekeeper enabled but make it ignore some applications, just run something like xattr -d com.apple.quarantine /Applications/SomeApp.app.