How to properly close a writeable file stream

[Matan Safriel]

Hi,

I'm a bit confused about closing a writeable file stream. See https://github.com/flatiron/winston/issues/423 - third and last comment.

Documentation says: 

Call this method when no more data will be written to the stream. 

Does this mean it is left to the application developer to track all write callbacks in order to determine the earliest time that .end can be called? 

Thanks!
Matan