Skip to content
ValgoValgoValgo

Valgo

Valgo
Valgo

Type-safe, expressive, and extensible Go validation library
with i18n support.

val := v.Is(
  v.String("Bob", "full_name").Not().Blank().LengthBetween(4, 20),
  v.Number(17, "age").GreaterThan(18),
)


if !val.Valid() {
  out, _ := json.MarshalIndent(val.ToError(), "", "  ")
  fmt.Println(string(out))
}
{
  "age": [
    "Age must be greater than \"18\""
  ],
  "full_name": [
    "Full name must have a length between \"4\" and \"20\""
  ]
}
Extended example

Compose ordinary Go functions into a complete registration flow with alternatives, dependent rules, and nested validation paths.

type Address struct {
  Line1      string
  City       string
  Country    string
  PostalCode string
}


type Registration struct {
  Name                 string
  Email                string
  Password             string
  PasswordConfirmation string
  ContactPreference    string
  ReferralCode         string
  Address              Address
}


func validateRegistration(input Registration) *v.Validation {
  return v.Is(
    v.String(input.Name, "name").Not().Blank().LengthBetween(2, 80),
    v.String(input.Email, "email").Not().Blank(),
    v.String(input.Password, "password").Not().Blank().LengthBetween(10, 64),
    v.String(input.ContactPreference, "contact_preference").
      EqualTo("email").Or().EqualTo("sms"),
    v.String(input.ReferralCode, "referral_code").
      Empty().OrElse().MatchingTo(regexp.MustCompile(`^[A-Z0-9]{6,12}$`)),
  ).IfPathValid("password",
    v.Is(v.String(input.PasswordConfirmation, "password_confirmation").
      EqualTo(input.Password)),
  ).In("address",
    v.Is(
      v.String(input.Address.Line1, "line1").Not().Blank(),
      v.String(input.Address.City, "city").Not().Blank(),
      v.String(input.Address.Country, "country").Not().Blank().EqualTo("US"),
      v.String(input.Address.PostalCode, "postal_code").Not().Blank(),
    ).WhenAllValid([]string{"country", "postal_code"}, func(val *v.Validation) {
      if err := verifyPostalCode("US", input.Address.PostalCode); err != nil {
        val.AddErrorMessage("postal_code", "Postal code could not be verified")
      }
    }),
  )
}
Installing
go get github.com/cohesivestack/valgo
Agent skill
npx skills add cohesivestack/valgo –skill valgo