please update to use db.model instead of mongoose.model

[daskyrk]

I'm submitting a...

[ ] Regression 
[x] Bug report
[x] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead post your question on Stack Overflow.

Current behavior

Some times the db command is hanging and returned promise will never resolve. It seems that we should use createConnection with db.model(...) and connect with mongoose.model(...).When i change to use connect, everything works fine, So maybe this plugin should update to prevent this case. please see: https://stackoverflow.com/questions/22786374/queries-hang-when-using-mongoose-createconnection-vs-mongoose-connect

Expected behavior

db command not hang

Minimal reproduction of the problem with instructions

What is the motivation / use case for changing the behavior?

it maybe difficult to reproduce my case, there is some log output:

  public create(docs: Partial<T>): Promise<T> {
    console.log('inner create: start');
    const pro = this._model.create(docs);
    console.log('inner create: end', pro);
    return pro;
  }

  public async createComment(data: CommentDto, req: Request) {
    console.log('create comment service:');
    const comment = await super.create(data);
    console.log('create comment service after:', comment);
}

// log: 
create comment service:
inner create: start
inner create: end Promise { <pending> } // hang there 
catch error in timeout interceptor:

Environment

Nest version: "@nestjs/core": "^6.0.4"
plugin version:  "@nestjs/mongoose": "^6.0.0"



For Tooling issues:
- Node version: v10.15.3  
- Platform:  Mac 

Others:

[kamilmysliwiec]

It seems that we should use createConnection with db.model(...)

Actually, we are using db.model:

useFactory: (connection: Connection) =>
      connection.model(model.name, model.schema, model.collection),

https://github.com/nestjs/mongoose/blob/master/lib/mongoose.providers.ts