I would like an API that exposes the mongoDB version being worked with.
Currently, (as far as I know) there is no way to obtain the connected mongo version.

For example, for critical paths that require atomicity I would like the application to be able to know what version of mongo we are connected to so I can use the transaction API, or fall back to primary preferred, majority write.

I started hacking away with the transactions API which unexpectedly failed miserably with a mongo serialization error on Mongo 3.6. Coming from the mgo driver, which has a transaction API, I inadvertently expected the mongo-driver API to also work for 3.6.