This is naive, no one ever turn telemetry on if it's turned off by default, that's the reason why it's on by default.

> no one ever turn telemetry on if it's turned off by default

If nobody would voluntarily do it, why do you think it's okay to do it at all? By your very admission, nobody wants this. Because if they did, they'd turn it on!

Still, opt-out is just inacceptable. At least with a mechanism which can easily fail, like setting an environment variable. This basically forces you to wrap the go tool in a script which ensures the environment variable to be set.

As this seem to cache the results, another option is to fiddle with the cache to report bogus information.

You can set env variable for the go toolchain with a command such as: go env -w TELEMETRY=off which will be written to disk and use by the go cli.

Where will it be written to and how is it guaranteed to be picked up by any further invocations of the tools?

Yeah, given go's history with breaking changes (and the habit of OKR-chasing managers and Senior Staff to make Number Go Up to look good on the promo packet), I definitely would not trust any opt-out mechanism to not receive operationally-significant changes in the next five years.

As far as I known go never changed any flags since release ( 2012 ), is it good enough for you?

"This is naïve, no one would ever allow me into their homes if I asked first, and how else would I find out what diseases they have?"