Make BasicFunc support dependency injection

[vpereira]

I was able to solve this problem, using db as global variable. However, would be better if I could pass it to my callback (that today, accepts just two params - user and password). Could you support a variable number of params, where I could for example pass the db handle? I stumbled many times in this question and either I found a "use another middlewear" or "set your db variable global"..

[attilaolah]

This is a little tricky because (I think) we would have to inject the username and password in the context as well in order for BasicFunc to be able to access it.

[vpereira]

maybe if the function accepts not 2 strings, but a struct, where at least includes the fields username and password?

[attilaolah]

No you can't do that with a struct.

You can, however, do that with an interface, but that seems like too much complexity. After all, you could just pass in the db in a closure. Or pass in a method to auth.BasicFunc, and have the method access the db via the struct.

func main() {
    // …
    m.Use(auth.BasicFunc(&(DBAuth{…}).Authenticate))
}

type DBAuth struct {
    // …
}

func (a *DBAuth) Authenticate(username, password string) bool {
    db := a.Database()
    // authenticate username and password using the db…
}

func (a *DBAuth) Database() *DB {
    return &DB{…}
}

…you get the idea.

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Summary: what you want can already be achieved without DI. I don't see a great need for DI here, but, if someone wants to implement this, why not. Just send a PR.