feature model interface (#222)

* make variable declaration more concise

* add model interface

* optimize interface methods

* fix: go test failed

* warp returns

* optimize

tools/goctl/model/sql/example/sql/user.sql

@@ -1,6 +1,7 @@
 -- 用户表 --
 CREATE TABLE `user` (
   `id` bigint(10) NOT NULL AUTO_INCREMENT,
+  `user` varchar(50) NOT NULL DEFAULT '' COMMENT '用户',
   `name` varchar(255) COLLATE utf8mb4_general_ci NOT NULL DEFAULT '' COMMENT '用户名称',
   `password` varchar(255) COLLATE utf8mb4_general_ci NOT NULL DEFAULT '' COMMENT '用户密码',
   `mobile` varchar(255) COLLATE utf8mb4_general_ci NOT NULL DEFAULT '' COMMENT '手机号',
@@ -10,6 +11,7 @@ CREATE TABLE `user` (
   `update_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
   PRIMARY KEY (`id`),
   UNIQUE KEY `name_index` (`name`),
+  UNIQUE KEY `user_index` (`user`),
   UNIQUE KEY `mobile_index` (`mobile`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;