Add s390x machine

[claucece]

This PR is still WP.

@armfazh , where did you get the sha for the golang image for the other machines?

[armfazh]

@armfazh , where did you get the sha for the golang image for the other machines?

I used arm64v8/golang:1.14.0 however, I looked for that image today and has a different sha value.
Maybe we must move to tags rather than shasum.

[armfazh]

I was investigating what happens with s390x, it seems fetching code causes invalid signature, hence one trick is to vendor dependencies. Include the vendor folder and the following:

Suggested change

	docker run --rm -v `pwd`:`pwd` -w `pwd` s390x/golang@$SHA256 go test -v ./...
	docker run --rm -v `pwd`:`pwd` -w `pwd` s390x/golang@$SHA256 go test -mod=vendor -v ./...

[claucece]

Mmm.. not a big fan of vendoring. I'll investigate tomorrow if there is an alternative.. if not, let's use vendor.

[claucece]

I used arm64v8/golang:1.14.0 however, I looked for that image today and has a different sha value.

Yeah, I also saw that. I'll see how it looks with tags ;)

[armfazh]

@claucece please take a look on #121. I did lots of changes to make it work.
The bug was raised by s390x because it is big endian. In some parts of the code, it always assumes little endian ordering.

[claucece]

Closing this PR as the other was merged.