Fix possible race in signal handler

sig/sig.go

@@ -39,6 +39,7 @@ func New(h SigReceivedHandler, sigs ...os.Signal) *Handler {
 
 func (h *Handler) Loop(ctx context.Context, cancel func()) error {
 	defer cancel()
+	defer signal.Stop(h.sigCh)
 
 	for {
 		select {

sig/sig_test.go

@@ -0,0 +1,100 @@
+package sig
+
+import (
+	"context"
+	"os"
+	"syscall"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+// TestLoopContextCancel verifies that Loop exits when the context is cancelled
+// and that signal.Stop is called (the channel no longer receives signals).
+func TestLoopContextCancel(t *testing.T) {
+	var received os.Signal
+	h := New(SigReceivedHandlerFunc(func(sig os.Signal) {
+		received = sig
+	}), syscall.SIGUSR1)
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	errCh := make(chan error, 1)
+	go func() {
+		errCh <- h.Loop(ctx, cancel)
+	}()
+
+	// Cancel the context to make Loop exit
+	cancel()
+
+	select {
+	case err := <-errCh:
+		require.ErrorIs(t, err, context.Canceled)
+	case <-time.After(5 * time.Second):
+		t.Fatal("Loop did not exit after context cancellation")
+	}
+
+	// After Loop returns, the signal channel should be deregistered.
+	// Sending SIGUSR1 to ourselves should NOT be received by the handler.
+	require.Nil(t, received, "handler should not have been called")
+
+	// Verify the channel is stopped: send a signal and confirm it doesn't
+	// arrive on the (now-stopped) channel.
+	syscall.Kill(syscall.Getpid(), syscall.SIGUSR1)
+	time.Sleep(50 * time.Millisecond)
+
+	select {
+	case _, ok := <-h.sigCh:
+		if ok {
+			t.Fatal("signal was delivered to channel after Loop returned — signal.Stop was not called")
+		}
+	default:
+		// Channel is empty — signal.Stop worked correctly
+	}
+}
+
+// TestLoopSignalReceived verifies that Loop calls the handler and exits
+// when a signal is received, and that signal.Stop is called afterward.
+func TestLoopSignalReceived(t *testing.T) {
+	var received os.Signal
+	h := New(SigReceivedHandlerFunc(func(sig os.Signal) {
+		received = sig
+	}), syscall.SIGUSR1)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	errCh := make(chan error, 1)
+	go func() {
+		errCh <- h.Loop(ctx, cancel)
+	}()
+
+	// Give Loop a moment to start
+	time.Sleep(50 * time.Millisecond)
+
+	// Send SIGUSR1 to ourselves
+	syscall.Kill(syscall.Getpid(), syscall.SIGUSR1)
+
+	select {
+	case err := <-errCh:
+		require.NoError(t, err)
+	case <-time.After(5 * time.Second):
+		t.Fatal("Loop did not exit after signal")
+	}
+
+	require.Equal(t, syscall.SIGUSR1, received, "handler should have received SIGUSR1")
+
+	// After Loop exits, send another signal — it should NOT be delivered
+	syscall.Kill(syscall.Getpid(), syscall.SIGUSR1)
+	time.Sleep(50 * time.Millisecond)
+
+	select {
+	case _, ok := <-h.sigCh:
+		if ok {
+			t.Fatal("signal was delivered to channel after Loop returned — signal.Stop was not called")
+		}
+	default:
+		// Channel is empty — signal.Stop worked correctly
+	}
+}