I don't want to keep a flate.Writer allocated for every connection due to memory usage. Instead, I'd rather store the rolling window myself and then grab a writer out of the pool and reset it with the window and then write a message to the connection.
I don't have plans to submit it to the stdlib unless someone expresses a need for it. The threshold for adding stuff is of course a bit higher for the stdlib.
Adding it to the functions above would not be super easy, since everything related to history was pulled out to make it stateless. OTOH is would also not be massive. Having, say a max 8K dict would be feasible, but every call would of course require it to be re-indexed, so not free.