fix: recycle ldap connections in pool

Signed-off-by: hongming <talonwan@yunify.com>

pkg/models/iam/im.go

@@ -467,6 +467,8 @@ func GetUserInfo(username string) (*models.User, error) {
 		return nil, err
 	}
 
+	defer conn.Close()
+
 	userSearchRequest := ldap.NewSearchRequest(
 		ldapclient.UserSearchBase,
 		ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 0, false,
@@ -1162,6 +1164,8 @@ func DescribeGroup(path string) (*models.Group, error) {
 		return nil, err
 	}
 
+	defer conn.Close()
+
 	groupSearchRequest := ldap.NewSearchRequest(searchBase,
 		ldap.ScopeSingleLevel, ldap.NeverDerefAliases, 0, 0, false,
 		fmt.Sprintf("(&(objectClass=posixGroup)(cn=%s))", cn),