refactor: graceful shutdown for server (#482)

backend/internal/utils/signals/signal.go

@@ -0,0 +1,40 @@
+package signals
+
+import (
+	"context"
+	"log"
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+/*
+This code is adapted from:
+https://github.com/kubernetes-sigs/controller-runtime/blob/8499b67e316a03b260c73f92d0380de8cd2e97a1/pkg/manager/signals/signal.go
+Copyright 2017 The Kubernetes Authors.
+License: Apache2 (https://github.com/kubernetes-sigs/controller-runtime/blob/8499b67e316a03b260c73f92d0380de8cd2e97a1/LICENSE)
+*/
+
+var onlyOneSignalHandler = make(chan struct{})
+
+// SignalContext returns a context that is canceled when the application receives an interrupt signal.
+// A second signal forces an immediate shutdown.
+func SignalContext(parentCtx context.Context) context.Context {
+	close(onlyOneSignalHandler) // Panics when called twice
+
+	ctx, cancel := context.WithCancel(parentCtx)
+
+	sigCh := make(chan os.Signal, 2)
+	signal.Notify(sigCh, os.Interrupt, syscall.SIGTERM)
+	go func() {
+		<-sigCh
+		log.Println("Received interrupt signal. Shutting down…")
+		cancel()
+
+		<-sigCh
+		log.Println("Received a second interrupt signal. Forcing an immediate shutdown.")
+		os.Exit(1)
+	}()
+
+	return ctx
+}