email validation code for Go. For test cases, refer https://gist.github.com/Crazy3lf/5cd87ae25fb21c92284b04201f1ffc5e

emailValidation.go

func isValidEmail(Value string) (result bool) {
	result = false
	var checkAllowed = regexp.MustCompile(`^[a-zA-z0-9_\-.+]+$`).MatchString

	i := strings.Index(Value, `@`)
	if i < 1 {
		return
	}
	if strings.Contains(Value, `..`) || strings.Contains(Value, `@@`) || strings.Contains(Value, `.@`) {
		return
	}
	if strings.IndexAny(Value, `.@`) == 0 {
		return
	}

	namePart := Value[:i]
	serverPart := Value[i+1:]
	if len(namePart) == 0 || len(serverPart) < 5 {
		return
	}

	// namePart surrounded by '"' is valid
	if strings.HasPrefix(namePart,`"`) && strings.HasSuffix(namePart,`"`){
		strings.Trim(namePart,`"`)
	}

	// serverPart cannot start with '-'
	if strings.HasPrefix(serverPart,`-`){
		return
	}

	// check the position of '.'
	i = strings.Index(serverPart, `.`)
	if i <= 0 || i > len(serverPart)-2{
		return
	}
	result = checkAllowed(namePart) && checkAllowed(serverPart)
	return
}