feat: filesystem store backend (#251)

* Update go.mod

* Update cookie.go

* add filesystem store as provided by Gorilla sessions

* Add filesystem backend example

* add filesystem tester

* add example file, add some debug output in tests

* reset package / module paths, so it should ready to merge

* module cleanup

* conflicts resolved, ready for review

* fix filesystem test

---------

Co-authored-by: Bo-Yi Wu <appleboy.tw@gmail.com>

Author: geschke

README.md

@@ -15,6 +15,7 @@ Gin middleware for session management with multi-backend support:
 - [GORM](#gorm)
 - [memstore](#memstore)
 - [PostgreSQL](#postgresql)
+- [Filesystem](#Filesystem)
 
 ## Usage
 
@@ -506,3 +507,40 @@ func main() {
   r.Run(":8000")
 }
 ```
+
+### Filesystem
+
+```go
+package main
+
+import (
+  "github.com/gin-contrib/sessions"
+  "github.com/gin-contrib/sessions/filesystem"
+  "github.com/gin-gonic/gin"
+)
+
+func main() {
+  r := gin.Default()
+
+  var sessionPath = "/tmp/" // in case of empty string, the system's default tmp folder is used
+
+  store := filesystem.NewStore(sessionPath,[]byte("secret"))
+  r.Use(sessions.Sessions("mysession", store))
+
+  r.GET("/incr", func(c *gin.Context) {
+    session := sessions.Default(c)
+    var count int
+    v := session.Get("count")
+    if v == nil {
+      count = 0
+    } else {
+      count = v.(int)
+      count++
+    }
+    session.Set("count", count)
+    session.Save()
+    c.JSON(200, gin.H{"count": count})
+  })
+  r.Run(":8000")
+}
+```

_example/filesystem/main.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	sessions "github.com/geschke/gin-contrib-sessions"
+	"github.com/geschke/gin-contrib-sessions/filesystem"
+	"github.com/gin-gonic/gin"
+)
+
+func main() {
+	sessionPath := "/tmp/"
+	r := gin.Default()
+	store := filesystem.NewStore(sessionPath, []byte("secret"))
+	r.Use(sessions.Sessions("mysession", store))
+
+	r.GET("/incr", func(c *gin.Context) {
+		session := sessions.Default(c)
+		var count int
+		v := session.Get("count")
+		if v == nil {
+			count = 0
+		} else {
+			count = v.(int)
+			count++
+		}
+		session.Set("count", count)
+		session.Save()
+		c.JSON(200, gin.H{"count": count})
+	})
+	r.Run(":8000")
+}

filesystem/filesystem.go

@@ -0,0 +1,31 @@
+package filesystem
+
+import (
+	"github.com/gin-contrib/sessions"
+	gsessions "github.com/gorilla/sessions"
+)
+
+type Store interface {
+	sessions.Store
+}
+
+// Keys are defined in pairs to allow key rotation, but the common case is to set a single
+// authentication key and optionally an encryption key.
+//
+// The first key in a pair is used for authentication and the second for encryption. The
+// encryption key can be set to nil or omitted in the last pair, but the authentication key
+// is required in all pairs.
+//
+// It is recommended to use an authentication key with 32 or 64 bytes. The encryption key,
+// if set, must be either 16, 24, or 32 bytes to select AES-128, AES-192, or AES-256 modes.
+func NewStore(path string, keyPairs ...[]byte) Store {
+	return &store{gsessions.NewFilesystemStore(path, keyPairs...)}
+}
+
+type store struct {
+	*gsessions.FilesystemStore
+}
+
+func (c *store) Options(options sessions.Options) {
+	c.FilesystemStore.Options = options.ToGorillaOptions()
+}

filesystem/filesystem_test.go

@@ -0,0 +1,40 @@
+package filesystem
+
+import (
+	"os"
+	"testing"
+
+	"github.com/gin-contrib/sessions"
+	"github.com/gin-contrib/sessions/tester"
+)
+
+var sessionPath = os.TempDir()
+
+var newStore = func(_ *testing.T) sessions.Store {
+	store := NewStore(sessionPath, []byte("secret"))
+	return store
+}
+
+func TestFilesystem_SessionGetSet(t *testing.T) {
+	tester.GetSet(t, newStore)
+}
+
+func TestFilesystem_SessionDeleteKey(t *testing.T) {
+	tester.DeleteKey(t, newStore)
+}
+
+func TestFilesystem_SessionFlashes(t *testing.T) {
+	tester.Flashes(t, newStore)
+}
+
+func TestFilesystem_SessionClear(t *testing.T) {
+	tester.Clear(t, newStore)
+}
+
+func TestFilesystem_SessionOptions(t *testing.T) {
+	tester.Options(t, newStore)
+}
+
+func TestFilesystem_SessionMany(t *testing.T) {
+	tester.Many(t, newStore)
+}