Refactor pmctl into new portmaster-start

cmds/portmaster-start/shutdown.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"sync"
+)
+
+var (
+	startupComplete = make(chan struct{}) // signal that the start procedure completed (is never closed, just signaled once)
+	shuttingDown    = make(chan struct{}) // signal that we are shutting down (will be closed, may not be closed directly, use initiateShutdown)
+	//nolint:deadcode,unused // false positive on linux, currently used by windows only
+	shutdownError error // protected by shutdownLock
+	shutdownLock  sync.Mutex
+)
+
+func initiateShutdown(err error) {
+	shutdownLock.Lock()
+	defer shutdownLock.Unlock()
+
+	select {
+	case <-shuttingDown:
+		return
+	default:
+		shutdownError = err
+		close(shuttingDown)
+	}
+}
+
+func isShutdown() bool {
+	select {
+	case <-shuttingDown:
+		return true
+	default:
+		return false
+	}
+}
+
+//nolint:deadcode,unused // false positive on linux, currently used by windows only
+func getShutdownError() error {
+	shutdownLock.Lock()
+	defer shutdownLock.Unlock()
+
+	return shutdownError
+}