Length counter fixed for emoji like multi byte characters (#152)

* Length counter fixed for emoji like multi byte characters

* Length counter fix tests are added for emoji containing strings

validate.go

@@ -24,7 +24,7 @@ func MaxLength(length int) Validator {
 	return func(val interface{}) error {
 		if str, ok := val.(string); ok {
 			// if the string is longer than the given value
-			if len(str) > length {
+			if len([]rune(str)) > length {
 				// yell loudly
 				return fmt.Errorf("value is too long. Max length is %v", length)
 			}
@@ -44,7 +44,7 @@ func MinLength(length int) Validator {
 	return func(val interface{}) error {
 		if str, ok := val.(string); ok {
 			// if the string is shorter than the given value
-			if len(str) < length {
+			if len([]rune(str)) < length {
 				// yell loudly
 				return fmt.Errorf("value is too short. Min length is %v", length)
 			}

validate_test.go

@@ -93,13 +93,27 @@ func TestMaxLength(t *testing.T) {
 	if err := MaxLength(140)(testStr); err == nil {
 		t.Error("No error returned with input greater than 150 characters.")
 	}
+
+	// emoji test
+	emojiStr := "I😍Golang"
+	// validate visible length with Maxlength
+	if err := MaxLength(10)(emojiStr); err != nil {
+		t.Errorf("Error returned with emoji containing 8 characters long input.")
+	}
 }
 
 func TestMinLength(t *testing.T) {
 	// validate the string
 	if err := MinLength(12)(randString(10)); err == nil {
 		t.Error("No error returned with input less than 12 characters.")
 	}
+
+	// emoji test
+	emojiStr := "I😍Golang"
+	// validate visibly 8 characters long string with MinLength
+	if err := MinLength(10)(emojiStr); err == nil {
+		t.Error("No error returned with emoji containing input less than 10 characters.")
+	}
 }
 
 func TestMinLength_onInt(t *testing.T) {