Level creates an option that sets the level of a ReadConcern.

Linearizable specifies that the query should return data that reflects all successful writes issued with a write concern of "majority" and acknowledged prior to the start of the read operation.

Local specifies that the query should return the instance’s most recent data.

Majority specifies that the query should return the instance’s most recent data acknowledged as having been written to a majority of members in the replica set.

New constructs a new read concern from the given string.

ReadConcern for replica sets and replica set shards determines which data to return from a query.

Option is an option to provide when creating a ReadConcern.