getCollaborators returns null

I have generated a personal access token and done the following code:
```
// Login
var git = new github({
token: github_token
})
var git_repo = git.getRepo(owner, repo)

// Get List Of Collaboraters
git_repo.getCollaborators(got_collaborators);
```
The `github_token` is my personal access token. The `owner` is my github username, and the `repo` is the name of my private repo. This is returning null even though there are ~10 collaborators on this project.

Googling around showed me that someone else had this problem and fixed it by adding `?affiliation=direct` and it solved it. There there an equivalent I can do here?

Start at the getCollaborators entry point and inspect how the repository collaborator request is formed. Compare its available options with the GitHub API's affiliation=direct behavior; done means collaborators for a private repository are returned instead of null.

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