kustomize build with remote resource may panic on slow networks

[johejo]

Describe the bug

At 6bbc829#diff-867c23b9f5a4ba53f94117fdfeb7c9899f849e5e231fee3d720fab5ceae43b9f
A timeout has been added to the getter.

But, due to improper handling of channels, writing to closed channels occurs at some point.

kustomize/api/loader/getter.go

Lines 97 to 111 in 67e445c

	ch := make(chan bool, 1)
	defer close(ch)
	d := 21 * time.Second // arbitrary
	timer := time.NewTimer(d)
	defer timer.Stop()
	go func() {
	err = client.Get()
	ch <- true
	}()
	select {
	case <-ch:
	case <-timer.C:
	err = types.NewErrTimeOut(d, "go-getter client.Get")
	}
	return err

If the call to client.Get exceeds 21 seconds (I don't know why this timeout value was chosen), the defer close(ch) closes the channel because the case for the timer finishes and returns.
After that, the background goroutine writes to the channel and panic occurs.

It does not occur every time.

Files that can reproduce the issue

Expected output

$ kustomize build "github.com/kubernetes-sigs/kustomize//examples/multibases"
piVersion: v1
kind: Pod
metadata:
  labels:
    app: myapp
  name: cluster-a-dev-myapp-pod
spec:
  containers:
  - image: nginx:1.7.9
    name: nginx
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    app: myapp
  name: cluster-a-prod-myapp-pod
spec:
  containers:
  - image: nginx:1.7.9
    name: nginx
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    app: myapp
  name: cluster-a-staging-myapp-pod
spec:
  containers:
  - image: nginx:1.7.9
    name: nginx

Actual output

$ kustomize build "github.com/kubernetes-sigs/kustomize//examples/multibases"
panic: send on closed channel

goroutine 9 [running]:
sigs.k8s.io/kustomize/api/loader.getRemoteTarget.func1(0xc00021e160, 0xc00021c610, 0xc000168070)
        /home/heijo/ghq/github.com/kubernetes-sigs/kustomize/api/loader/getter.go:104 +0x65
created by sigs.k8s.io/kustomize/api/loader.getRemoteTarget
        /home/heijo/ghq/github.com/kubernetes-sigs/kustomize/api/loader/getter.go:102 +0x446
exit status 2

Kustomize version

• 67e445c
• kustomize/v3.9.0

Platform

LInux

Additional context

[johejo]

Although not directly related to this issue, the variable err may be assigned from multiple goroutines at the same times, so it seems to be a race condition.

[monopole]

Thanks for the issue report @johejo , you're correct on all points.

[monopole]

fixed in #3400