Go 1.11 & 1.12 Docker images are not working anymore

[merlimat]

Motivation

CI is currently broken because the go mod download is failing in the docker images for Go 1.11 and 1.12.

go: gopkg.in/check.v1@v1.0.0-20190902080502-41f04d3bba15: git fetch -f origin refs/heads/*:refs/heads/* refs/tags/*:refs/tags/* in /pkg/mod/cache/vcs/7e5fa1eab4705eb80c9746632736cea906708d060702d529df6241d1c8c2c9f9: exit status 128:
	fatal: unable to access 'https://gopkg.in/check.v1/': server certificate verification failed. CAfile: none CRLfile: none
go: gopkg.in/check.v1@v1.0.0-20180628173108-788fd7840127: unknown revision 788fd7840127

The issue is related with Let's Encrypt root CA getting changed. Apparently the go tool is not even using the updated certs from the image.

Removing 1.11 and 1.12 from CI and adding newer versions 1.15, 1.16 and 1.17.