Adding methods to Oak's Context?

I am trying to figure out how to configure my Oak application/router so that my routes can do things like ctx.customMethod()ctx.customMethod(), could someone point me in the right direction? I can only really find how to customize the StateState, but that would only let me do ctx.state.customMethod()ctx.state.customMethod() – is that how you're supposed to do it instead of what I had in mind?