I think the link should be changed to the 1.15 release notes (now published): https://golang.org/doc/go1.15 -- these are much more interesting and useful.
> I'm curious which package managers / repositories allow you to update to the latest version of go as soon as it's released * ?
Arch Linux.
I just saw the release when I was checking for updated versions of packages I maintain, and built it before users started bugging me about outdated go binaries.
I continue to love how this works out with security updates too. I usually get new browser and kernel versions after particularly bad CVEs within a few hours from the upstream release.
NixOS and Nixpkgs. They are not instant updates in most cases like Arch, but Unstable has quite a few updated packages, and everything or anything can be updated or held back without fear of breaking, as previous config is a simple reboot away.
As one commenter pointed out, you could use a rolling release distro like Arch or Fedora Rawhide and get the latest packages within days (sometimes hours) of the official release. I run vanilla Fedora and am usually at most six months behind the last release (though the GHC package is quite behind on Fedora, IIRC).
The snap distribution: https://snapcraft.io/go . The 1.15/stable channel is already up, and I expect the default latest/stable channel will switch in short order.
Snap is only good if you don't mind getting forced updates at any time, and no ability to pin versions without going to great lengths. You can't even control when the updates get installed. I avoid it like the plague.
Move up a rolling pre-release like Debian/testing and things are available quite quickly. You can pin packages to limit what you’ll run the latest of.
Or if you do not and you like official releases, you can use some of the services like https://newreleases.io to get notification and install using official installer.