Can not set server-side authentication headers

The following comment suggests that this is possible, but I've spent the better part of the last 3 hours trying every trick in the book and can't find any solutions. Is this supported? We can't monkey patch it since it's not exported, but that seems excessive anyway. What is the expected use-case that this comment refers to?

https://github.com/adamsoffer/next-apollo/blob/master/src/withApollo.js#L181-L182

Thanks a bunch =^.^=