Fixed review comments

Fixed running as a windows service
Added logging to windows evenlog

syslog_windows.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"log"
+	"strings"
+
+	"golang.org/x/sys/windows"
+	"golang.org/x/sys/windows/svc/eventlog"
+)
+
+// should be the same as the service name!
+const eventLogSrc = "AdGuardHome"
+
+type eventLogWriter struct {
+	el *eventlog.Log
+}
+
+// Write sends a log message to the Event Log.
+func (w *eventLogWriter) Write(b []byte) (int, error) {
+	return len(b), w.el.Info(1, string(b))
+}
+
+func configureSyslog() error {
+	// Continue if we receive "registry key already exists" or if we get
+	// ERROR_ACCESS_DENIED so that we can log without administrative permissions
+	// for pre-existing eventlog sources.
+	if err := eventlog.InstallAsEventCreate(eventLogSrc, eventlog.Info|eventlog.Warning|eventlog.Error); err != nil {
+		if !strings.Contains(err.Error(), "registry key already exists") && err != windows.ERROR_ACCESS_DENIED {
+			return err
+		}
+	}
+	el, err := eventlog.Open(eventLogSrc)
+	if err != nil {
+		return err
+	}
+
+	log.SetOutput(&eventLogWriter{el: el})
+	return nil
+}