Using/Creating Metrics in extension

Hello all,

I’m working on a tls.Dial type extension. I have it correctly sending and receiving, however the DataSent and DataReceived metrics are both showing 0 bytes. I would also like to create more granular metrics like handShakeTime and waitingForResponseTime. Looking at the docs for NewMetric didn’t really clear things up for me.

So my questions are: How can I use those 2 built-in metrics? Given some data, how can I implement my own metric?