diff --git a/go.mod b/go.mod
index 5196420..209ffed 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,7 @@ module github.com/debug-ing/validation-go
 
 go 1.22.3
 
-require github.com/google/uuid v1.6.0
+require (
+	github.com/google/uuid v1.6.0
+	github.com/oklog/ulid/v2 v2.1.0
+)
diff --git a/go.sum b/go.sum
index 7790d7c..3f7a479 100644
--- a/go.sum
+++ b/go.sum
@@ -1,2 +1,5 @@
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/oklog/ulid/v2 v2.1.0 h1:+9lhoxAP56we25tyYETBBY1YLA2SaoLvUFgrP2miPJU=
+github.com/oklog/ulid/v2 v2.1.0/go.mod h1:rcEKHmBBKfef9DhnvX7y1HZBYxjXb0cP5ExxNsTT1QQ=
+github.com/pborman/getopt v0.0.0-20170112200414-7148bc3a4c30/go.mod h1:85jBQOZwpVEaDAr341tbn15RS4fCAsIst0qp7i8ex1o=
diff --git a/main.go b/main.go
index cd73931..da5c4c0 100644
--- a/main.go
+++ b/main.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"fmt"
 
 	"github.com/debug-ing/validation-go/pkg/validation"
@@ -12,6 +13,7 @@ type UpdateIAMUserRequest struct {
 	LName string `validate:"required,minlength=10"`
 	Age   int    `validate:"required,numeric,minmax=18-100"`
 	Nike  string `validate:"required,between=1-10"`
+	KOS   string `validate:"test"`
 }
 
 func main() {
@@ -22,11 +24,20 @@ func main() {
 		Age:   29,
 		Nike:  "sdfkjdf",
 	}
-	//
+	validation.AddCustomValidator("test", "%s vard kon", validateRequired)
 	err := validation.ValidateStruct(req)
 	if err != nil {
 		fmt.Println("Validation error:", err)
 	} else {
 		fmt.Println("Validation passed")
 	}
+	//
+}
+
+func validateRequired(value string, errorMsg string) error {
+	if value == "" {
+		fmt.Println(errorMsg)
+		return errors.New(errorMsg)
+	}
+	return nil
 }
diff --git a/pkg/validation/rules.go b/pkg/validation/rules.go
index fb1c565..23e9ca4 100644
--- a/pkg/validation/rules.go
+++ b/pkg/validation/rules.go
@@ -2,10 +2,12 @@ package validation
 
 import (
 	"errors"
+	"regexp"
 	"strconv"
 	"strings"
 
 	"github.com/google/uuid"
+	"github.com/oklog/ulid/v2"
 )
 
 func validateRequired(value string, errorMsg string) error {
@@ -23,6 +25,38 @@ func validationIsUUID(value string, errorMsg string) error {
 	return nil
 }
 
+func validationIsULID(value string, errorMsg string) error {
+	_, err := ulid.Parse(value)
+	if err != nil {
+		return errors.New(errorMsg)
+	}
+	return nil
+}
+
+func validationIsBIC(value string, errorMsg string) error {
+	bicRegex := `^[A-Za-z]{4}[A-Za-z]{2}[A-Za-z0-9]{2}([A-Za-z0-9]{3})?$`
+	if matched, _ := regexp.MatchString(bicRegex, value); !matched {
+		return errors.New(errorMsg)
+	}
+	return nil
+}
+
+func validationIsEthereumAddress(value string, errorMsg string) error {
+	ethRegex := `^0x[a-fA-F0-9]{40}$`
+	if matched, _ := regexp.MatchString(ethRegex, value); !matched {
+		return errors.New(errorMsg)
+	}
+	return nil
+}
+
+func validationIsBtcAddress(value string, errorMsg string) error {
+	btcRegex := `^(1|3|bc1)[a-zA-HJ-NP-Z0-9]{25,39}$`
+	if matched, _ := regexp.MatchString(btcRegex, value); !matched {
+		return errors.New(errorMsg)
+	}
+	return nil
+}
+
 func validateMinLength(value string, min int, errorMsg string) error {
 	if len(value) < min {
 		return errors.New(errorMsg)
diff --git a/pkg/validation/validator.go b/pkg/validation/validator.go
index b3b3d4d..c8bae78 100644
--- a/pkg/validation/validator.go
+++ b/pkg/validation/validator.go
@@ -101,6 +101,14 @@ func ValidateStruct(s interface{}) error {
 	return nil
 }
 
+func AddCustomValidator(tagName, message string, fn interface{}) {
+	validators[tagName] = fn
+	data[tagName] = map[string]string{
+		"error_msg": message,
+	}
+	fmt.Println(data)
+}
+
 func getMessage(tagName, fieldName string, args ...interface{}) string {
 	errorMsgTemplate := data[tagName]["error_msg"]
 	return fmt.Sprintf(errorMsgTemplate, append([]interface{}{fieldName}, args...)...)