EXAMPLE GO CUSTOM VALIDATOR

// NOTED: if value or key is exist in mapping = error
// NOTED: if value or key is not exist in mapping = not error
// more validation struct reference follow this link -> https://github.com/go-playground/validator

// example usage
package main

import (
    "fmt"
    util "github.com/restuwahyu13/customvalidator/utils"
)

type User struct {
    Fullname       string     `validate:"required,lowercase"`
    Email          string     `validate:"required,email"`
}

func main() {
    var input User

    input.Fullname = "Restu Wahyu Saputra"
    input.Email = "restuwahyu13@#zetmail.com"

    resultErr := util.GoValidator(input)

    if resultErr["Fullname"] == "" {
      fmt.Println("Fullname is required")
      return
    }

    if resultErr["Email"] == "" {
      fmt.Println("Emai is required")
      return
    }

    if resultErr["Fullname"] == "Restu Wahyu Saputra" {
      fmt.Println("Fullname must be lowercase not camelcase")
      return
    }

    if resultErr["Email"] == "restuwahyu13@#zetmail.com" {
      fmt.Println("Emai is not valid")
      return
    }
}

// example custom validator
package util

import "github.com/go-playground/validator/v10"

var validate *validator.Validate

func GoValidator(s interface{}) map[string]interface{} {

    validate = validator.New()

    err := validate.Struct(s)
    errObject := make(map[string]interface{})

    if err != nil {
        for _, errResult := range  err.(validator.ValidationErrors) {
            errObject[errResult.StructField()] = errResult.Value()
        }
    }

    return errObject
}