Add signals package

this provides a simple way to handle incoming
os signas using context

Signed-off-by: adrianc <adrianc@nvidia.com>

pkg/signals/signals.go

@@ -0,0 +1,45 @@
+// Copyright (c) 2024 Multus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package signals provides handling for os signals.
+package signals
+
+import (
+	"context"
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+var onlyOneSignalHandler = make(chan struct{})
+
+// SetupSignalHandler registers for SIGTERM and SIGINT. A context is returned
+// which is canceled on one of these signals. If a second signal is caught, the program
+// is terminated with exit code 1.
+func SetupSignalHandler() context.Context {
+	close(onlyOneSignalHandler) // panics when called twice
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	c := make(chan os.Signal, 2)
+	signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)
+	go func() {
+		<-c
+		cancel()
+		<-c
+		os.Exit(1) // second signal. Exit directly.
+	}()
+
+	return ctx
+}