Replace already closed github.com/golang/mock with go.uber.org/mock

[forsaken628]

What this PR does / why we need it:

github.com/golang/mock already closed

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #2356

Checklist:

• Docs included if any changes are user facing

[tenzen-y]

@forsaken628 One question here, do we need to introduce https://github.com/uber/mock/blob/v0.4.0/gomock/controller.go#L116 the as we discussed here?: #2350 (comment)

[forsaken628]

It's a bit more rigorous when WithOverridableExpectations is introduced, always gomock.InOrder makes it work too.

[tenzen-y]

@forsaken628 It seems that the e2e tests often failed due to webhook server startup.
I was supposed to add the custom readiness check in the #2345 like the training-operator: https://github.com/kubeflow/training-operator/blob/9a9edecf146bb0c2cccaeb3bec912ab2dfa5d8c5/cmd/training-operator.v1/main.go#L230-L247

So, could you open PR to implement such a custom readiness chack mechanism to the katib controller?

[tenzen-y]

It's a bit more rigorous when WithOverridableExpectations is introduced, always gomock.InOrder makes it work too.

Uhm, that makes sense.
Let's revisit here once we need to add the more strict verifications since the current implementations align with the previous implementations.

[tenzen-y]

Anyway, this PR still lgtm
/lgtm
/approve

[google-oss-prow]

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