go: failed generating correct code

[sakura-rip]

when running below command, frugal -gen=go:async hoge.frugal

The generated file will raise Unresolved reference 'ctx' Error

https://github.com/Workiva/frugal/blob/daacef7dce45875fdf620095f03dc06a920664b3/compiler/generator/golang/generator.go#L1979

This location is wrong.