JSON parse error when using OAuth token

I've got this to work using Postman, however the following code generates a JSON parse error?

## Code
```js
const graphql = require('graphql.js');
const graph = graphql('https://api.github.com/graphql', {
method: "POST",
headers: {
"User-Agent": "node",
"Authorization": "Bearer "
}
});

const query = graph(`query { viewer { login name } }`);

query().then(
res => console.log(JSON.stringify(res)),
err => console.error(err)
);
```

## Error

```sh
{ message: 'Problems parsing JSON',
documentation_url: 'https://developer.github.com/v4' }
```