func (m *memData) GetCredencial(tipo string) interface{} {
    m.l.RLock()
    defer m.l.RUnlock()

    // Recibo un struct {admin: { user:somevalue1, pass:somevalue2}, mongo: { ... }, }
    locals := getLocals()

    // NOTE: encontrar una mejor manerar de hacer esto
    switch tipo {
    case "admin":
        return locals.Admin
    default:
        return errors.New("not found")
    }
}

func getLocals() Locals {
    locals := Locals{}
    file, _ := os.Open("./locals.json")
    defer file.Close()
    json.NewDecoder(file).Decode(&locals)

    return locals
}