True, but beware of the domain name you're using. Because VeriSign may unilaterally decide to delete your domain name along with thousands of others [1] and you're back to square one…
Deepcopy [1] is a Go package that is still heavily used despite its creator has disappeared 9 years ago. At least GitHub is a stable and trusted host as a distribution point and communication point for users.
Signed modules / including the signature hash would also solve a lot, e.g. it'd mean domain sales no longer silently inherit full permissions. It's sorta a shame that Go keeps doing such a good job at a minimum-viable wheel-rewrite, but then lets it linger for so long without catching up to the rest of the programming world.
How many mainstream languages have content addressed imports? I can’t think of any, so I assume I’m misunderstanding your meaning of the term because you seem to be suggesting that it is common and Go is the outlier for lacking it?
Which keeps happening with stuff they rebuild from scratch - an excellent and somewhat unique first showing, far beyond what most first attempts manage, but followed by near-complete stagnation while issues that everyone familiar with the field predicted from miles away pile up.
Which is a shame because there is quite a lot to like about Go in practice. And in spite of it all I'm thrilled that it is eating into Python's share in a lot of places.
You already can use SHA in go.mod in exactly the same way you would use a version string.
I don’t know about using multiple proxies in go mod though.
And while the go.sum file in a module is returned by proxy.golang.org (somewhat surprisingly), that only includes the module's dependencies, not itself. So you're still stuck trusting a goproxy to serve you the correct data.
If github is "taken down" you can't just resolve the whole domain differently, you need to only resolve the packages differently. If your "Golang domain" is taken down, it should be a lot easier to hotfix until something proper is implemented (the quickest and dirtiest would be a hostfile-entry).
It is being retired because very few people use it. It kind of sucks but this is how domains work, it’s not real estate.