cmd/go: suggest 'go get' instead of 'go mod tidy' when indirect dependencies are missing

[bcmills]

(Noticed while testing #45979.)

If a lazy module (#36460) is missing explicit requirements on indirect dependencies, we currently emit the error message:

go: updates to go.mod needed; to update it:
	go mod tidy

This advice is correct, but it's too big a hammer — we should instead suggest go get on the specific packages within the main repo whose transitive dependencies are missing.

CC @jayconrod @matloob

[dwertent]

@bcmills I'm encountering this issue. How do you recommend I approach this issue until it's fixed? how can I know what module is the problematic one?
Thank you

[meetme2meat]

@bcmills we are facing the similar problem all our CI test for golang 1.17 are failing with exact same error, downgraded the go version on drone.yml to 1.16 seem to work. Is there any specific that need to done to have our test working under go 1.17

[bcmills]

@dwertent, @meetme2meat: this issue is about changing which command we suggest when the go.mod file is inconsistent; the go mod tidy command that we suggest today is correct, it just makes more changes than are strictly necessary to resolve the condition. (This is a UX issue, not a bug to be fixed or worked around.)

[meetme2meat]

@bcmills Understood, but now our Drone CI running under go 1.17 result in failure(and work when go 1.16) with the exact same message. I don't know why it exiting at the above test as on my machine it work correctly

[bcmills]

Run go mod tidy, as the error message says, and then commit the result. If that doesn't resolve the error, please file a new issue from the issue template (https://golang.org/issue/new).

[bcmills]

(CC @matloob @samthanawalla)