useNewUrlParser , useUnifiedTopology , useFindAndModify , and useCreateIndex are no longer supported options. Mongoose 6 always behaves as if useNewUrlParser , useUnifiedTopology , and useCreateIndex are true , and useFindAndModify is false .
Mongoose version 6.0 이상이면
useNewUrlParser : true,
useUnifiredTopology : true,
useCreateIndex : true,
useFindAndModify : false
이게 기본값이기 때문에 지원을 안함.
無汗不成(무한불성) : 땀을 흘리지 않고는 이룰 수 없다.