JSON

Structs in, JSON out

The app didn't want the text Hello — it wanted data: a list of walkers with names and prices, as JSON. Go's encoding/json package converts between your Go structs and JSON, and it's built into the standard library like everything else.

The rule of thumb: your server holds data as structs (typed, checked by the compiler) and speaks JSON on the wire. encoding/json is the translator in the middle.