Basically I have a Go server which parses some XML file and creates a structure with the data which I want to send over TCP to an IOS app.
At the moment I tried to use Protocol Buffers, but I am having problems with this on the IOS side. So from your experience is this the best way I should transmit my data ? Any other suggestions ?
The first thing I am looking for it's speed.
There is no best way. There are plenty of cross-platform serialization formats out there. Just pick the one you are the most comfortable with, and which suits your needs.
An obvious choice is json (human readable and well supported on all platforms).
If you favor speed, then have a look at msgpack: