cmd/go: invalid module: gopkg.in/inf.v0 should be .v0, not v1 (v1.9.1-gopkgin-v0.9.1)

[krasi-georgiev]

go1.12.1 linux/amd64

go test github.com/jaegertracing/jaeger/plugin/storage/badger/dependencystore -run ^(TestDependencyReader)$ 

go: github.com/gocql/gocql@v0.0.0-20180506184654-181004e14a3f: parsing go.mod: go.mod:6: invalid module: gopkg.in/inf.v0 should be .v0, not v1 (v1.9.1-gopkgin-v0.9.1)
go: error loading module requirements

[andybons]

@bcmills @jayconrod

[bcmills]

I can reproduce the error; still investigating why it occurs. (I need to rebuild to pick up @jayconrod's new module-loader diagnostics!)

[bcmills]

The error comes directly from an old version of github.com/gocql/gocql that does indeed specify an invalid version:
https://github.com/gocql/gocql/blob/611715ed8a5e3a3165dd2609e4e3c8ff7d0c774e/go.mod#L6

So the diagnostic message as reported is correct, and probably as precise as we can make it.

That version of github.com/gocql/gocql comes in by conversion of the existing jaeger/Gopkg.lock:
https://github.com/jaegertracing/jaeger/blob/7da22606eccbb4246f7cd2f3871ec6b491257b68/Gopkg.lock#L303

To fix jaegertracing/jaeger, it suffices to remove and re-resolve the gocql dependency:

jaeger$ go1.12.1 mod init github.com/jaegertracing/jaeger
go: creating new go.mod: module github.com/jaegertracing/jaeger
go: copying requirements from Gopkg.lock

jaeger$ go1.12.1 mod edit -droprequire=github.com/gocql/gocql

jaeger$ go1.12.1 mod tidy
go: finding github.com/onsi/ginkgo/extensions/table latest
go: finding github.com/prashantv/protectmem latest
go: finding github.com/streadway/quantile latest
go: finding github.com/bmizerany/perks/quantile latest
go: finding github.com/onsi/ginkgo/extensions latest
go: finding github.com/bmizerany/perks latest
go: finding github.com/gocql/gocql latest
go: finding github.com/bitly/go-hostpool latest
go: finding github.com/bmizerany/assert latest

jaeger$ go1.12.1 build ./...

jaeger$

This is somewhat related to #26454 and #30831, in that it should be possible to upgrade past the error (using go get github.com/gocql/gocql@latest) rather than removing and re-resolving the dependency. Today that does not work, because the error in resolving the initial gopkg.in/inf.v0 causes the whole operation to fail before the upgrades are attempted.

[bcmills]

Closing as a duplicate of #30831: the symptoms are a bit different, but the underlying pathology (having an existing bad dependency and not being able to upgrade out of it) will probably be fixed by the same set of changes.