checker/doc/normalizers/lower.md

Lower Case Normalizer

The lower normalizer maps all Unicode letters in the given value to their lower case. It can be mixed with checkers and other normalizers when defining the validation steps for user data.

type User struct {
  Username string `checkers:"lower"`
}

user := &User{
  Username: "chECker",
}

checker.Check(user)

fmt.Println(user.Username) // checker