signaler: improve cross-platform signal compatibility (#1952)

* signaler: improve cross-platform signal compatibility

- Add runtime-based platform detection for signal handling
- Include os.Kill only on Windows (cannot be caught/ignored on Unix)
- Refactor signal initialization into separate getPlatformSignals function

* signaler: add dependency injection and improve docs

- Introduce SignalNotifier interface for testability
- Add osSignalNotifier implementation and factory function
- Enhance package and function documentation
- Maintain backward compatibility with existing API

* [signaler] simplify shutdown handling; drop SIGABRT/os.Kill

* skip signaler tests on windows

* support signaler interrupt tests and improve signal handling tests

* removing getPlatformSignal function

* remove signaler readme

* Signaler: Return a channel from WaitForInterrupt

* Signaler: fix comment

Co-authored-by: Ryan O'Hara-Reid <oharareid.ryan@gmail.com>

* Signaler: require NoError to NoErrorf

Co-authored-by: Ryan O'Hara-Reid <oharareid.ryan@gmail.com>

---------

Co-authored-by: Ryan O'Hara-Reid <oharareid.ryan@gmail.com>

signaler/signaler.go

@@ -1,3 +1,4 @@
+// Package signaler provides cross-platform signal handling for graceful application shutdown
 package signaler
 
 import (
@@ -6,20 +7,9 @@ import (
 	"syscall"
 )
 
-var s = make(chan os.Signal, 1)
-
-func init() {
-	sigs := []os.Signal{
-		os.Interrupt,
-		os.Kill,
-		syscall.SIGTERM,
-		syscall.SIGABRT,
-	}
-	signal.Notify(s, sigs...)
-}
-
-// WaitForInterrupt waits until a os.Signal is
-// received and returns the result
-func WaitForInterrupt() os.Signal {
-	return <-s
+// WaitForInterrupt returns a channel to receive termination signals
+func WaitForInterrupt() chan os.Signal {
+	c := make(chan os.Signal, 1)
+	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
+	return c
 }

signaler/signaler_test.go

@@ -0,0 +1,37 @@
+package signaler
+
+import (
+	"os"
+	"runtime"
+	"syscall"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestWaitForInterrupt(t *testing.T) {
+	t.Parallel()
+	for _, sig := range []os.Signal{syscall.SIGTERM, os.Interrupt} {
+		sigC := WaitForInterrupt()
+		proc, err := os.FindProcess(os.Getpid())
+		require.NoError(t, err, "os.FindProcess must not error")
+
+		if err := proc.Signal(sig); err != nil {
+			if runtime.GOOS == "windows" {
+				t.Skipf("proc.Signal(%s) not supported on Windows: %v", sig, err)
+			}
+			require.NoErrorf(t, err, "proc.Signal(%s) must not error", sig)
+		}
+
+		assert.Eventuallyf(t, func() bool {
+			select {
+			case got := <-sigC:
+				return got == sig
+			default:
+				return false
+			}
+		}, 2*time.Second, 10*time.Millisecond, "Signal %s should be received within timeout", sig)
+	}
+}