Is there a centralized place to access response Content-Length for telemetry

I want to add telemetry either as a log or to Application insights for the Content-Length of a response in dotnet core 2.2. I've tried a number of places in middleware and different filters in the request pipeline. No where that I've checked has the Content-Length materialized--it's always null.

My alternate solution was to check the response stream myself and compute the length but I'd really prefer not to re-read the stream if I don't have to. Is there somewhere in the dotnet core request pipeline that I can hook into for that information?