title: Why is FindOne where id using typeorm and mongodb doesn't work?
body: <p>I am using typeorm with MongoDB. When I am searching for a document by Id with this syntax
  <code>const manager = getMongoManager(); const user = await manager.findOne(User, {userId});</code> I got undefined result and when I use <code>const manager = getMongoManager(); const user = await manager.findOne(User, {});</code> I got the result with userId expected in the first syntax.</p>
  <p>Besides the same syntax works fine with any other criteria other than Id.</p>
  <p>The declaration of the Id in the model is: <code>@ObjectIdColumn({ name: '_id' }) @IsNotEmpty() public userId: ObjectID;</code></p>
  <p>For now, I have only one user in the database with the userId that I search for.</p>
  <p>Where could be the problem? And how to resolve that?</p>