fix: mockapiserver data race in create memorystorage

[yuwenma]

What this PR does / why we need it:
This PR fixes a data race issue in test where two threads in MockKubeAPIserver memorystorage read/write to the same resourceInformation

** Verify**
With this PR, the following command should no longer give the data race warning (see data race log)

 go test -race sigs.k8s.io/kubebuilder-declarative-pattern/pkg/patterns/declarative

data race log

WARNING: DATA RACE
Write at 0x00c000792d50 by goroutine 112:
  runtime.mapaccessK()
      /usr/local/go/src/runtime/map.go:518 +0x1ec
  sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver.(*MemoryStorage).CreateObject()
      /Users/yuwenma/go/src/sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver/memorystorage.go:194 +0x204
  sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver.(*postResource).Run()
      /Users/yuwenma/go/src/sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver/postresource.go:72 +0x3d4
  sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver.(*MockKubeAPIServer).ServeHTTP()
      /Users/yuwenma/go/src/sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver/apiserver.go:334 +0x4680
  net/http.serverHandler.ServeHTTP()
      /usr/local/go/src/net/http/server.go:2936 +0x548
  net/http.(*conn).serve()
      /usr/local/go/src/net/http/server.go:1995 +0x8d8
  net/http.(*Server).Serve.func3()
      /usr/local/go/src/net/http/server.go:3089 +0x4c

Previous read at 0x00c000792d50 by goroutine 93:
  runtime.mapdelete()
      /usr/local/go/src/runtime/map.go:695 +0x47c
  sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver.(*resourceStorage).watch()
      /Users/yuwenma/go/src/sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver/memorystorage_watch.go:68 +0x3a8
  sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver.(*MemoryStorage).Watch()
      /Users/yuwenma/go/src/sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver/memorystorage_watch.go:23 +0x42c
  sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver.(*listResource).doWatch()
      /Users/yuwenma/go/src/sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver/listresource.go:111 +0x378
  sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver.(*listResource).Run()
      /Users/yuwenma/go/src/sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver/listresource.go:61 +0x188
  sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver.(*MockKubeAPIServer).ServeHTTP()
      /Users/yuwenma/go/src/sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver/apiserver.go:334 +0x4680
  net/http.serverHandler.ServeHTTP()
      /usr/local/go/src/net/http/server.go:2936 +0x548
  net/http.(*conn).serve()
      /usr/local/go/src/net/http/server.go:1995 +0x8d8
  net/http.(*Server).Serve.func3()
      /usr/local/go/src/net/http/server.go:3089 +0x4c

Goroutine 112 (running) created at:
  net/http.(*Server).Serve()
      /usr/local/go/src/net/http/server.go:3089 +0x620
  sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver.(*MockKubeAPIServer).StartServing.func1()
      /Users/yuwenma/go/src/sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver/apiserver.go:66 +0x68

Goroutine 93 (running) created at:
  net/http.(*Server).Serve()
      /usr/local/go/src/net/http/server.go:3089 +0x620
  sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver.(*MockKubeAPIServer).StartServing.func1()
      /Users/yuwenma/go/src/sigs.k8s.io/kubebuilder-declarative-pattern/mockkubeapiserver/apiserver.go:66 +0x68

Which issue(s) this PR fixes:

[yuwenma]

/assign @justinsb

[justinsb]

Thanks for fixing. If we ever do a higher-performance version of the storage, we should snapshot objects to avoid locking everything during the initial stream of objects. But this isn't intended as a high performance mock, so safe & correct is good here!

Not sure if we need a rebase to pick up you go 1.20 fix, I'll try to trigger a retest.

/approve
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: justinsb, yuwenma

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[justinsb]

Thanks for rebasing

/lgtm