部分公共代码db和const放到shared目录

shared/db/BaseModel.ts

@@ -0,0 +1,24 @@
+import { prop, pre } from '@typegoose/typegoose';
+
+/**
+  * BaseModel
+*/
+@pre<BaseModel>('save', function(next) {
+  if (!this.createdAt || this.isNew) {
+    this.createdAt = this.updatedAt = new Date();
+  } else {
+    this.updatedAt = new Date();
+  }
+  next();
+})
+
+export default class BaseModel {
+
+  _id?: string
+
+  @prop()
+  createdAt: Date
+
+  @prop()
+  updatedAt: Date
+}