Add option to produce private structs for query params

[kazhuravlev]

We use sqlc to generate some code, and on top of that, we write others.

But unfortunately, generated code and structs are available by other packages. Also, different packages can see New and Queries. So in the next PR, I would like to add corresponding options.

[kyleconroy]

If the query structs are private, how are you calling the methods?

[kazhuravlev]

Good point.

I try to explain what I am expecting.

storage/
- query.sql
- db.gen.go
- models.gen.go
- queries.gen.go
- public_api_of_my_service.go

I want to generate queries by sqlc to some packages, like storage. Also, this package will contain some hand-written code (public_api_of_my_service.go). When my clients consume storage functionality - they will use only methods in public_api_of_my_service.go.

So, they call some hand-write public method (like GetSomeObjectByID()), and this method will use code-generated code produced by sqlc.

[kazhuravlev]

@kyleconroy, do you have any comments on that?

[kyleconroy]

By using an internal package you can get the same level of encapsulation. Take a look at the attached example, but if you put an internal package inside your storage package, only the storage package can access it.

example
├── go.mod
├── query.sql
├── sqlc.json
├── storage
│   ├── internal
│   │   └── db
│   │       ├── db.go
│   │       ├── models.go
│   │       └── query.sql.go
│   └── service.go
└── web
    └── main.go

example.zip