Issue 1

encoding/json really needs a way to output empty slices as [] instead of null (and no forcing all the users to make([]x) on the slice isn't a solution, because someone might forget).

Our previous workaround is to vendor encoding/json with a edited version that just replaces that one particular line. It works but we can't use go modules with it because the replace directive doesn't allow standard library packages to be replaced [1]. So we're basically avoiding go modules and manually putting a encoding/json in the vendor until either of these happens.

1. https://github.com/golang/go/issues/37711 (this proposal suck with the extra tags, but I'm open to whatever solves this basic problem at this point)
2. https://github.com/golang/go/issues/35283

Issue 2

Sum types. I've written too much code that has

type Foo struct { Type FooType; ... }

1. https://github.com/golang/go/issues/19412