//create struct register form
type UserRegister struct {
    Email    string    `validate:"required,max=20,min=8"`
    Password string `validate:"required,max=20,min=8"`
    Captcha  string `validate:"required,captcha"`
}

//method Insert for UserRegister struct if validation success
func (u *UserRegister) Insert() {
    //код вставки
}

//validate -> insert
func Controller(n *N) {
    var userRegister UserRegister
    err := validator.Validate(&userRegister)
    if err == nil {
        userRegister.Insert()
    }
}

//Main struct User
type User struct {
   Id       int
   Email    string
   Password string
   Active   int
   //another fields from user table
}

//methods for work with User: user.Insert(), user.SelectById() etc.
func (u *UserRegister) Insert() {
    //insert code
}
func (u *UserRegister) IsUniqueEmail() {
    //check unique code
}

//struct for validation register form
type UserRegister struct {
    Email    string    `validate:"required,max=20,min=8"`
    Password string `validate:"required,max=20,min=8"`
    Captcha  string `validate:"required,captcha"`
}

//validate userRegister if succeess -> transfer data to main user struct -> insert
func Controller(n *N) {
    var userLogin UserRegister
    err := validator.Validate(&userRegister)
    if err == nil {
        //transfer data from userRegister to user
        user := User{
           Email:       userRegister.Email,
           Password: userRegister.Password,
           ...
        }
        //insert
        user.Insert()
    }
}