This fixes the EOF error once and for all. It was my fault all along :(
See Go issue: http://code.google.com/p/go/issues/detail?id=3514 This solution is kind of racy since we're not guaranteed to be using the same connection again when we retry, but it seems to work in practice.
This matches the README example. Also, use the new array-based POST format. (Forgot about this one before.)