proposal: go get -u to notify about new major versions

[lzap]

Proposal Details

The standard Go tooling currently does not provide any indication that there was a major version release of a module depdency. The generic workflow that is spread around the internet is to simply do go get -u an you are good. My concern is that many projects can easily get stuck on older versions of modules forever without people even noticing that.

We briefly discussed this on Slack where I was asking about a tool that would show major version releases for a project and immediately a community user replied with "just use go get -u" which is obviously not correct. This confirms the concern that we need go get -u to inform users about this. I believe this should be the default behavior with command line argument to turn this off. By the way such projects do exist, however, it did not work for me (an unknown error) and it does not solve the visibility concern.

I am not proposing to write a tool which would help with upgrading, that would be nice but not on the table right now. All I am proposing is the following workflow:

$ go get -u ./...
go: downloading github.com/module/xyz v1.0.1
note: new github.com/module/v3/abc major version available

This will get people curious enough to investigate what is going on and what needs to be done in order to upgrade. Thanks for taking a look into this.

[lzap]

On dupe of #40323 sorry did not find it.