Update client-go to v12.0.0

[shaneutt]

What should be cleaned up or changed:

Currently if you want to include kind as a library in another tool it will hold your client-go version at v11.0.0 by default. The latest release for client-go is now v12.0.0 and it would be helpful to update kind to this version.

Why is this needed:

This makes it a bit easier to integrate with kind as a library.

[BenTheElder]

Relatedly please know that the library form is significantly less stable, @munnerz and I have been working on a plan to clear that up, expect future versions of the library to change quite a bit.

We export much more than we should.

[shaneutt]

Thanks for the heads up @BenTheElder, currently I only have a lightweight integration. I will be cautious about going deeper with that integration. 👍

[BenTheElder]

We're still working on the library interface but it's actively coming along 😅

I beleive #744 removed client-go from being tracked here.

[shaneutt]

When trying current master it seems that #744 didn't stop client-go from getting pulled in at v11.0.0+incompatible when kind is used as a library.

In case others run into this I've just been using a simple workaround in my go.mod with the replace verb e.g.:

replace k8s.io/client-go v11.0.0+incompatible => k8s.io/client-go v0.0.0-20190819141724-e14f31a72a77

[BenTheElder]

thanks!

I admit i've not imported a recent version of kind into another project yet, I'm currently working on refining the library surface and usability more.

I think the replace is probably the right solution long term, it looks like we'll want to actually start using client go for #850 in the future possibly...