// external network in parallel. If non-nil, it contains one buffer slot per
// test (send to acquire), with a low enough limit that the overall number of
// connections (summed across subprocesses) stays at or below base.NetLimit.
var netTestSem chan struct{}

var exeSuffix string = func() string {
	if runtime.GOOS == "windows" {
		return ".exe"
	}
	return ""
}()

func tooSlow(t *testing.T, reason string) {