Watch external directory

Is there a way to watch external directories (outside the current project)

Like:

```yaml
pattens:
- '**/*.go'
- '**/*.yml'
- '$GOPATH/src/gitlab.com/my-library/**/*.go'
```

I am building some packages that live outside the project, and I want to have my project restart when those files are changed

It may be I just have the incorrect syntax