我正在学习NestJs，并尝试使用Mongoose与MongoDB（本地）集成。
从这里得到的想法：https://medium.com/globant/crud-application-using-nestjs-and-mongodb-99a0756adb76
我做了一个自己的应用程序，叫做coupon-service：https://github.com/ductruong253/coupon-service/tree/feature/db-config
但是当我尝试启动应用程序时，出现了一个错误：

[Nest] 21089  - 05/05/2023, 12:25:36 AM     LOG [NestFactory] Starting Nest application...
[Nest] 21089  - 05/05/2023, 12:25:37 AM   ERROR [ExceptionHandler] Cannot read properties of undefined (reading 'tree')
TypeError: Cannot read properties of undefined (reading 'tree')
    at Model.Document.$__setSchema (/media/truongdd/ubuntu/learning/git/coupon-service/node_modules/mongoose/lib/document.js:3452:18)
    at Model.Document (/media/truongdd/ubuntu/learning/git/coupon-service/node_modules/mongoose/lib/document.js:88:10)
    at new Model (/media/truongdd/ubuntu/learning/git/coupon-service/node_modules/mongoose/lib/model.js:121:12)
    at Injector.instantiateClass (/media/truongdd/ubuntu/learning/git/coupon-service/node_modules/@nestjs/core/injector/injector.js:351:19)
    at callback (/media/truongdd/ubuntu/learning/git/coupon-service/node_modules/@nestjs/core/injector/injector.js:56:45)
    at Injector.resolveConstructorParams (/media/truongdd/ubuntu/learning/git/coupon-service/node_modules/@nestjs/core/injector/injector.js:136:24)
    at Injector.loadInstance (/media/truongdd/ubuntu/learning/git/coupon-service/node_modules/@nestjs/core/injector/injector.js:61:13)
    at Injector.loadProvider (/media/truongdd/ubuntu/learning/git/coupon-service/node_modules/@nestjs/core/injector/injector.js:88:9)
    at /media/truongdd/ubuntu/learning/git/coupon-service/node_modules/@nestjs/core/injector/instance-loader.js:56:13
    at async Promise.all (index 4)

此错误的可能原因是什么以及如何修复它？
谢啦
丹