CI: install specific version of golang for cross build

[medyagh]

currently the cross build script on jenkins, uses whatever golang available on the master,

to minimize variances,
I recommend we pin down the version to use same golang verison both in travis and jenkins

the cross build script in jenkins should check for go version, if not available install it.
https://github.com/kubernetes/minikube/blob/master/hack/jenkins/minikube_cross_build_and_upload.sh

Currently I set the travis version to 1.12.7
we need to set it in jenkins too

[afbjorklund]

So this means we should build more of minikube in docker ? Or did you have another plan here ?

Seems to be using quite different methods now, random Travis-image vs random Jenkins-install :

matrix:
  include:
    - go: 1.12.7

declare -rx GOPATH=/var/lib/jenkins/go

currently the cross build script on jenkins, uses whatever golang available on the master,

It seems that most builds, are using the version that is in the "kube-cross:v1.12.5" image.

# NOTE: "latest" as of 2019-05-09. kube-cross images aren't updated as often as Kubernetes
BUILD_IMAGE 	?= k8s.gcr.io/kube-cross:v1.12.5-1

So far I can see a gofmt call, that is not respecting the BUILD_IN_DOCKER variable.

[afbjorklund]

Maybe it is enough to update the BUILD_IMAGE ?

https://github.com/kubernetes/kubernetes/tree/master/build/build-image/cross

kubernetes/kubernetes@dfa46f8

FROM golang:1.12.7

[afbjorklund]

Building the kvm2 driver uses the go version from the host. Maybe that was a bad idea ?

Need to set GO_VERSION, when building in CI at least.

GO_VERSION ?= $(shell go version | cut -d' ' -f3 | sed -e 's/go//')

Anyway, that is where the 1.12.5 in the logs is coming from.

docker build --build-arg "GO_VERSION=1.12.5" -t gcr.io/k8s-minikube/kvm-build-image -f installers/linux/kvm/Dockerfile installers/linux/kvm/

[afbjorklund]

I believe that everything should use the docker version of go now, is there anything else ?

$ docker run k8s.gcr.io/kube-cross:v1.12.7-1 go version
go version go1.12.7 linux/amd64

Travis is somewhat different, it uses the gimme tool: https://github.com/travis-ci/gimme

[afbjorklund]

For reference, here are the Docker images that are used:

https://github.com/kubernetes/kubernetes/blob/master/build/build-image/cross/Dockerfile

REPOSITORY              TAG                 IMAGE ID            CREATED             SIZE
k8s.gcr.io/kube-cross   v1.12.7-1           3903d94c7b57        2 weeks ago         1.75GB

and indirectly https://github.com/docker-library/golang/blob/master/1.12/stretch/Dockerfile

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
golang              1.12.7-stretch      f50db16df5da        2 weeks ago         774MB

The go binary distribution is from https://golang.org/dl/