leader election panic: nil pointer deref

[alexec]

k8s.io/apimachinery/pkg/util/runtime.HandleCrash(0x0, 0x0, 0x0)
--
  | goroutine 129 [running]:
  | [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x19d03dc]
  | panic: runtime error: invalid memory address or nil pointer dereference
  | panic: runtime error: invalid memory address or nil pointer dereference [recovered]
  | /go/src/github.com/argoproj/argo-workflows/workflow/controller/controller.go:241 +0xfb8
  | created by github.com/argoproj/argo-workflows/v3/workflow/controller.(*WorkflowController).Run
  | /go/pkg/mod/k8s.io/client-go@v0.19.6/tools/leaderelection/leaderelection.go:222 +0x9c
  | k8s.io/client-go/tools/leaderelection.RunOrDie(0x206d8e0, 0xc00011fc40, 0x2079ce0, 0xc001e20500, 0x37e11d600, 0x2540be400, 0x12a05f200, 0xc0002118c0, 0xc001615c40, 0xc0015efd90, ...)
  | /go/pkg/mod/k8s.io/client-go@v0.19.6/tools/leaderelection/leaderelection.go:210 +0x15d
  | k8s.io/client-go/tools/leaderelection.(*LeaderElector).Run(0xc0016b8120, 0x206d8e0, 0xc001c6a100)
  | /go/pkg/mod/k8s.io/client-go@v0.19.6/tools/leaderelection/leaderelection.go:200 +0x29
  | k8s.io/client-go/tools/leaderelection.(*LeaderElector).Run.func1(0xc0016b8120)
  | /go/src/github.com/argoproj/argo-workflows/workflow/controller/controller.go:256 +0x7c
  | github.com/argoproj/argo-workflows/v3/workflow/controller.(*WorkflowController).Run.func2()
  | /usr/local/go/src/runtime/panic.go:969 +0x1b9
  | panic(0x1b6fb20, 0x2c9ca80)
  | /go/pkg/mod/k8s.io/apimachinery@v0.19.6/pkg/util/runtime/runtime.go:48 +0x89
  | k8s.io/apimachinery/pkg/util/runtime.HandleCrash(0x0, 0x0, 0x0)
  | /go/pkg/mod/k8s.io/apimachinery@v0.19.6/pkg/util/runtime/runtime.go:74 +0x95

[alexec]

				OnStoppedLeading: func() {
					logCtx.Info("stopped leading")
					cancel()
				},

cancel is nil.

[alexec]

Looking at the code, cancel is never set. It is always nil. StopLeading will always panic.

Because we have ReleaseOnCancel, We need

ctx, cancel := context.WithCancel(ctx)
	defer cancel()

As the second line of (wfc *WorkflowController) Run.

[alexec]

Looking at the code, cancel is never set. It is always nil. StopLeading will always panic.

Because we have ReleaseOnCancel, We need

ctx, cancel := context.WithCancel(ctx)
	defer cancel()

As the second line of (wfc *WorkflowController) Run.