后台：增加后台数据库表，修复连接问题

shared/db/GMUserGroup.ts

@@ -1,5 +1,5 @@
 import BaseModel from './BaseModel';
-import { index, getModelForClass, prop, DocumentType } from '@typegoose/typegoose';
+import { index, getModelForClass, prop, DocumentType, ReturnModelType, mongoose } from '@typegoose/typegoose';
 
 /**
   * GM账号和用户组关系接口
@@ -32,6 +32,11 @@ export default class GMUserGroup extends BaseModel {
   }
 }
 
-export const GMUserGroupModel = getModelForClass(GMUserGroup);
+export let GMUserGroupModel: ReturnModelType<typeof GMUserGroup, {}>;
+export function loadGMUserGroupModel(connect: mongoose.Connection) {
+  GMUserGroupModel = getModelForClass(GMUserGroup, {
+        existingConnection: connect
+    });
+}
 
 export interface GMUserGroupType extends Pick<DocumentType<GMUserGroup>, keyof GMUserGroup>{};