Cannot download go modules without go proxy

[amisevsk]

Describe the problem

It's not possible to download go modules without using proxy.golang.org due to a couple of issues:

• Running go mod download in the current master gives the error

  go: github.com/eclipse/che-plugin-broker@v3.1.1-0.20200207223144-b20597f15e4c+incompatible: invalid version: unknown revision b20597f15e4c
  

• replacing v3.1.1-0.20200207223144-b20597f15e4c+incompatible with v3.1.1 in the go.mod file and running again updates the dependency to

  require github.com/eclipse/che-plugin-broker v3.1.1+incompatible
  

  and outputs the error

  go: github.com/openshift/api@v3.9.1-0.20190424152011-77b8897ec79a+incompatible: invalid pseudo-version: preceding tag (v3.9.0) not found
  

  which is related to Fix dependency on github.com/openshift/api operator-framework/operator-lifecycle-manager#1241, though it appears that this should not apply to this project since we're using operator-sdk 0.17

Additional details

The default go package in Fedora 31 and 32 uses GOPROXY=direct, which causes the issue above; this will likely impact rhel-based distros as well.

Workaround

Set GOPROXY=https://proxy.golang.org,direct before downloading modules or download and use a separate binary -- e.g.

pushd $(mktemp -d)
go get golang.org/dl/go${VERSION}
go${VERSION} download
alias go=go${VERSION}
popd

Once modules have been successfully cached, the error above is avoided even without using proxy.golang.org

[amisevsk]

Additional context: openshift/api#456