func TestCause(t *testing.T) {
	var (
		forever       = 1e6 * time.Second
		parentCause   = fmt.Errorf("parentCause")
		childCause    = fmt.Errorf("childCause")
		tooSlow       = fmt.Errorf("tooSlow")
		finishedEarly = fmt.Errorf("finishedEarly")
	)
	for _, test := range []struct {
		name  string
		ctx   func() Context
		err   error
		cause error
	}{
		{
			name:  "Background",
			ctx:   Background,
			err:   nil,