> To opt out, users would set GOTELEMETRY=off in their environment or run a simple command like go env -w GOTELEMETRY=off; The first telemetry report is not sent until at least one week after installation, giving ample time to opt out. Opting out stops all collection and reporting: no “opt out” event is sent. It is simply impossible to see systems that install Go and then opt out in the next seven days.

Source: https://research.swtch.com/telemetry-intro