package main import ( "fmt" "gopkg.in/go-playground/validator.v9" ) // User contains user information type User struct { FirstName string `validate:"required"` LastName string `validate:"required"` Age uint8 `validate:"gte=0,lte=130"` Email string `validate:"required,email"` FavouriteColor string `validate:"iscolor"` // alias for 'hexcolor|rgb|rgba|hsl|hsla' Addresses []*Address `validate:"required,dive,required"` // a person can have a home and cottage... } // Address houses a users address information type Address struct { Street string `validate:"required"` City string `validate:"required"` Planet string `validate:"required"` Phone string `validate:"required"` } // use a single instance of Validate, it caches struct info var validate *validator.Validate func main() { validate = validator.New() validateStruct() validateVariable() } func validateStruct() { address := &Address{ Street: "Eavesdown Docks", Planet: "Persphone", Phone: "none", } user := &User{ FirstName: "Badger", LastName: "Smith", Age: 135, Email: "Badger.Smith@gmail.com", FavouriteColor: "#000-", Addresses: []*Address{address}, } // returns nil or ValidationErrors ( map[string]*FieldError ) err := validate.Struct(user) if err != nil { // this check is only needed when your code could produce // an invalid value for validation such as interface with nil // value most including myself do not usually have code like this. if _, ok := err.(*validator.InvalidValidationError); ok { fmt.Println(err) return } for _, err := range err.(validator.ValidationErrors) { fmt.Println(err.Namespace()) fmt.Println(err.Field()) fmt.Println(err.StructNamespace()) // can differ when a custom TagNameFunc is registered or fmt.Println(err.StructField()) // by passing alt name to ReportError like below fmt.Println(err.Tag()) fmt.Println(err.ActualTag()) fmt.Println(err.Kind()) fmt.Println(err.Type()) fmt.Println(err.Value()) fmt.Println(err.Param()) fmt.Println() } // from here you can create your own error messages in whatever language you wish return } // save user to database } func validateVariable() { myEmail := "joeybloggs.gmail.com" errs := validate.Var(myEmail, "required,email") if errs != nil { fmt.Println(errs) // output: Key: "" Error:Field validation for "" failed on the "email" tag return } // email ok, move on }