Nit: they don't do that anymore, because cross-origin caches cause privacy problems. But they used to, and this news is still percolating through the industry.

Some of them still do, if someone is using an outdated enough browser :D for example Chrome <86 (released 2020).

Didn't expect that, but not very surprised. So short of the browser giving the Go runtime some special treatment, this sounds like a no-go.