Mismatch of the tutorial section of stringsvc example and its full code

### What would you like?

I have noticed a couple of differences between the tutorial section of the [stringsvc3](https://gokit.io/examples/stringsvc.html#calling-other-services) example and its [full source code](https://github.com/go-kit/examples/tree/master/stringsvc3). It is worth mentioning the differences are about different `imports`, or different number of parameters of a particular function.
I was wondering which one is the most up to date one?