Golang Email Validation ; your choices.

main.go

package main

import (
	"fmt"
	"net/mail"

	"github.com/fatih/color"
	"github.com/go-playground/validator/v10"
)

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

func main() {
	users := []User{
		{Email: "simple.valid.email@email.test"},             // valid -1
		{Email: "simple.valid.email@sub1.sub2.email.test"},   // valid -2
		{Email: "simple.valid.email@email.test."},            // valid too (?) -3
		{Email: "simple.valid.email@sub1..sub2..email.test"}, // valid too (?) -4
		{Email: "simple.valid.email@email.test.."},           // invalid -1
		{Email: "simple.valid.email@.email.test"},            // invalid -2
		{Email: "simple.valid.email.@email.test"},            // invalid -3
		{Email: "simple.valid.email@email.test_"},            // invalid -4
		{Email: "simple.valid.email@email.test`"},            // invalid -5
		{Email: "simple.valid.email@email..test"},            // invalid -6
		{Email: "simple.valid..email@email.test"},            // invalid -7
		{Email: ".simple.valid.email@email.test"},            // invalid -8
		{Email: "..simple.valid.email@email.test"},           // invalid -9
	}

	fmt.Println("\nusing github.com/go-playground/validator/v10")
	for _, user := range users {
		validate := validator.New()
		if err := validate.Struct(&user); err != nil {
			printInvalid(user.Email, err.Error())
			continue
		}
		printValid(user.Email)
	}

	fmt.Println("\n\nusing net/mail")
	for _, user := range users {
		_, err := mail.ParseAddress(user.Email)
		if err != nil {
			printInvalid(user.Email, err.Error())
			continue
		}
		printValid(user.Email)
	}
}

func printValid(email string) {
	color.Green("email is valid, email: " + email)
}

func printInvalid(email, errMsg string) {
	color.New(color.FgHiRed).Println(errMsg, ", email:", email)
}