Support systemd socket-activation

Co-authored-by: Michael <michael.matur@gmail.com>

pkg/server/socket_activation_unix.go

@@ -0,0 +1,24 @@
+//go:build !windows
+
+package server
+
+import (
+	"net"
+
+	"github.com/coreos/go-systemd/activation"
+	"github.com/rs/zerolog/log"
+)
+
+func populateSocketActivationListeners() {
+	listenersWithName, _ := activation.ListenersWithNames()
+
+	socketActivationListeners = make(map[string]net.Listener)
+	for name, lns := range listenersWithName {
+		if len(lns) != 1 {
+			log.Error().Str("listenersName", name).Msg("Socket activation listeners must have one and only one listener per name")
+			continue
+		}
+
+		socketActivationListeners[name] = lns[0]
+	}
+}