feature: expired sessions can be deleted via a background goroutine.

- Call defer store.StopCleanup(store.Cleanup(time.Minute * 5)) after store creation.
- Does not break the existing API (optional, but recommended)
- Based on https://github.com/yosssi/boltstore/reaper
- Deletes expired sessions (where expireson > now())
- Includes tests

cleanup_test.go

@@ -0,0 +1,51 @@
+package pgstore
+
+import (
+	"net/http"
+	"os"
+	"testing"
+	"time"
+)
+
+func TestCleanup(t *testing.T) {
+	ss := NewPGStore(os.Getenv("PGSTORE_TEST_CONN"), []byte(secret))
+	if ss == nil {
+		t.Fatal("This test requires a real database")
+	}
+
+	defer ss.Close()
+	// Start the cleanup goroutine.
+	defer ss.StopCleanup(ss.Cleanup(time.Millisecond * 500))
+
+	req, err := http.NewRequest("GET", "http://www.example.com", nil)
+	if err != nil {
+		t.Fatal("Failed to create request", err)
+	}
+
+	session, err := ss.Get(req, "newsess")
+	if err != nil {
+		t.Fatal("Failed to create session", err)
+	}
+
+	// Expire the session
+	session.Options.MaxAge = 1
+
+	m := make(http.Header)
+	if err = ss.Save(req, headerOnlyResponseWriter(m), session); err != nil {
+		t.Fatal("failed to save session:", err.Error())
+	}
+
+	// Give the ticker a moment to run
+	time.Sleep(time.Second * 1)
+
+	// SELECT expired sessions. We should get a zero-length result slice back.
+	var results []int64
+	_, err = ss.DbMap.Select(&results, "SELECT id FROM http_sessions WHERE expireson < now()")
+	if err != nil {
+		t.Fatalf("failed to select expired sessions from DB: %v", err)
+	}
+
+	if len(results) > 0 {
+		t.Fatalf("ticker did not delete expired sessions: want 0 got %v", len(results))
+	}
+}