Because dozens of in between layers don't need to know the type, and should in fact work regardless of the specific type. Context tells you enough: someone, so

Because dozens of in between layers don't need to know the type, and should in fact work regardless of the specific type. Context tells you enough: someone, somewhere may do magic with this if you pass it down the chain. And in good Go tradition it's explicit about this: functions that don't take a context don't (generally) do that kind of magic. If anything it mixes two concerns: cancelation and dynamic scoping. But I'm not sure having two different parameters would be better.