Strengthens the session's function

 package session
 
 import (
+	"errors"
+	"io"
 	"io/ioutil"
 	"os"
 	"path"
@@ -48,6 +50,14 @@ func (fs *FileSessionStore) Delete(key interface{}) error {
 	return nil
 }
 
+func (fs *FileSessionStore) Flush() error {
+	fs.lock.Lock()
+	defer fs.lock.Unlock()
+	fs.values = make(map[interface{}]interface{})
+	fs.updatecontent()
+	return nil
+}
+
 func (fs *FileSessionStore) SessionID() string {
 	return fs.sid
 }
@@ -121,6 +131,55 @@ func (fp *FileProvider) SessionGC() {
 	filepath.Walk(fp.savePath, gcpath)
 }
 
+func (fp *FileProvider) SessionRegenerate(oldsid, sid string) (SessionStore, error) {
+	err := os.MkdirAll(path.Join(fp.savePath, string(oldsid[0]), string(oldsid[1])), 0777)
+	if err != nil {
+		println(err.Error())
+	}
+	err = os.MkdirAll(path.Join(fp.savePath, string(sid[0]), string(sid[1])), 0777)
+	if err != nil {
+		println(err.Error())
+	}
+	_, err = os.Stat(path.Join(fp.savePath, string(sid[0]), string(sid[1]), sid))
+	var newf *os.File
+	if err == nil {
+		return nil, errors.New("newsid exist")
+	} else if os.IsNotExist(err) {
+		newf, err = os.Create(path.Join(fp.savePath, string(sid[0]), string(sid[1]), sid))
+	}
+
+	_, err = os.Stat(path.Join(fp.savePath, string(oldsid[0]), string(oldsid[1]), oldsid))
+	var f *os.File
+	if err == nil {
+		f, err = os.OpenFile(path.Join(fp.savePath, string(oldsid[0]), string(oldsid[1]), oldsid), os.O_RDWR, 0777)
+		io.Copy(newf, f)
+	} else if os.IsNotExist(err) {
+		newf, err = os.Create(path.Join(fp.savePath, string(sid[0]), string(sid[1]), sid))
+	} else {
+		return nil, err
+	}
+	f.Close()
+	os.Remove(path.Join(fp.savePath, string(oldsid[0]), string(oldsid[1])))
+	os.Chtimes(path.Join(fp.savePath, string(sid[0]), string(sid[1]), sid), time.Now(), time.Now())
+	var kv map[interface{}]interface{}
+	b, err := ioutil.ReadAll(newf)
+	if err != nil {
+		return nil, err
+	}
+	if len(b) == 0 {
+		kv = make(map[interface{}]interface{})
+	} else {
+		kv, err = decodeGob(b)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	newf, err = os.OpenFile(path.Join(fp.savePath, string(sid[0]), string(sid[1]), sid), os.O_WRONLY|os.O_CREATE, 0777)
+	ss := &FileSessionStore{f: newf, sid: sid, values: kv}
+	return ss, nil
+}
+
 func gcpath(path string, info os.FileInfo, err error) error {
 	if err != nil {
 		return err

@@ -40,6 +40,13 @@ func (st *MemSessionStore) Delete(key interface{}) error {
 	return nil
 }
 
+func (st *MemSessionStore) Flush() error {
+	st.lock.Lock()
+	defer st.lock.Unlock()
+	st.value = make(map[interface{}]interface{})
+	return nil
+}
+
 func (st *MemSessionStore) SessionID() string {
 	return st.sid
 }
@@ -80,6 +87,29 @@ func (pder *MemProvider) SessionRead(sid string) (SessionStore, error) {
 	return nil, nil
 }
 
+func (pder *MemProvider) SessionRegenerate(oldsid, sid string) (SessionStore, error) {
+	pder.lock.RLock()
+	if element, ok := pder.sessions[oldsid]; ok {
+		go pder.SessionUpdate(oldsid)
+		pder.lock.RUnlock()
+		pder.lock.Lock()
+		element.Value.(*MemSessionStore).sid = sid
+		pder.sessions[sid] = element
+		delete(pder.sessions, oldsid)
+		pder.lock.Unlock()
+		return element.Value.(*MemSessionStore), nil
+	} else {
+		pder.lock.RUnlock()
+		pder.lock.Lock()
+		newsess := &MemSessionStore{sid: sid, timeAccessed: time.Now(), value: make(map[interface{}]interface{})}
+		element := pder.list.PushBack(newsess)
+		pder.sessions[sid] = element
+		pder.lock.Unlock()
+		return newsess, nil
+	}
+	return nil, nil
+}
+
 func (pder *MemProvider) SessionDestroy(sid string) error {
 	pder.lock.Lock()
 	defer pder.lock.Unlock()

@@ -50,6 +50,14 @@ func (st *MysqlSessionStore) Delete(key interface{}) error {
 	return nil
 }
 
+func (st *MysqlSessionStore) Flush() error {
+	st.lock.Lock()
+	defer st.lock.Unlock()
+	st.values = make(map[interface{}]interface{})
+	st.updatemysql()
+	return nil
+}
+
 func (st *MysqlSessionStore) SessionID() string {
 	return st.sid
 }
@@ -108,6 +116,28 @@ func (mp *MysqlProvider) SessionRead(sid string) (SessionStore, error) {
 	return rs, nil
 }
 
+func (mp *MysqlProvider) SessionRegenerate(oldsid, sid string) (SessionStore, error) {
+	c := mp.connectInit()
+	row := c.QueryRow("select session_data from session where session_key=?", oldsid)
+	var sessiondata []byte
+	err := row.Scan(&sessiondata)
+	if err == sql.ErrNoRows {
+		c.Exec("insert into session(`session_key`,`session_data`,`session_expiry`) values(?,?,?)", oldsid, "", time.Now().Unix())
+	}
+	c.Exec("update session set `session_key`=? where session_key=?", sid, oldsid)
+	var kv map[interface{}]interface{}
+	if len(sessiondata) == 0 {
+		kv = make(map[interface{}]interface{})
+	} else {
+		kv, err = decodeGob(sessiondata)
+		if err != nil {
+			return nil, err
+		}
+	}
+	rs := &MysqlSessionStore{c: c, sid: sid, values: kv}
+	return rs, nil
+}
+
 func (mp *MysqlProvider) SessionDestroy(sid string) error {
 	c := mp.connectInit()
 	c.Exec("DELETE FROM session where session_key=?", sid)

@@ -35,6 +35,11 @@ func (rs *RedisSessionStore) Delete(key interface{}) error {
 	return err
 }
 
+func (rs *RedisSessionStore) Flush() error {
+	_, err := rs.c.Do("DEL", rs.sid)
+	return err
+}
+
 func (rs *RedisSessionStore) SessionID() string {
 	return rs.sid
 }
@@ -99,6 +104,16 @@ func (rp *RedisProvider) SessionRead(sid string) (SessionStore, error) {
 	return rs, nil
 }
 
+func (rp *RedisProvider) SessionRegenerate(oldsid, sid string) (SessionStore, error) {
+	c := rp.connectInit()
+	if str, err := redis.String(c.Do("HGET", oldsid, oldsid)); err != nil || str == "" {
+		c.Do("HSET", oldsid, oldsid, rp.maxlifetime)
+	}
+	c.Do("RENAME", oldsid, sid)
+	rs := &RedisSessionStore{c: c, sid: sid}
+	return rs, nil
+}
+
 func (rp *RedisProvider) SessionDestroy(sid string) error {
 	c := rp.connectInit()
 	c.Do("DEL", sid)

 package session
 
 import (
+	"crypto/hmac"
+	"crypto/md5"
 	"crypto/rand"
+	"crypto/sha1"
 	"encoding/base64"
+	"encoding/hex"
 	"fmt"
 	"io"
 	"net/http"
@@ -16,11 +20,13 @@ type SessionStore interface {
 	Delete(key interface{}) error     //delete session value
 	SessionID() string                //back current sessionID
 	SessionRelease()                  // release the resource
+	Flush() error                     //delete all data
 }
 
 type Provider interface {
 	SessionInit(maxlifetime int64, savePath string) error
 	SessionRead(sid string) (SessionStore, error)
+	SessionRegenerate(oldsid, sid string) (SessionStore, error)
 	SessionDestroy(sid string) error
 	SessionGC()
 }
@@ -44,40 +50,91 @@ type Manager struct {
 	cookieName  string //private cookiename
 	provider    Provider
 	maxlifetime int64
+	hashfunc    string //support md5 & sha1
+	hashkey     string
 	options     []interface{}
 }
 
+//options
+//1. is https  default false
+//2. hashfunc  default sha1
+//3. hashkey default beegosessionkey
+//4. maxage default is none
 func NewManager(provideName, cookieName string, maxlifetime int64, savePath string, options ...interface{}) (*Manager, error) {
 	provider, ok := provides[provideName]
 	if !ok {
 		return nil, fmt.Errorf("session: unknown provide %q (forgotten import?)", provideName)
 	}
 	provider.SessionInit(maxlifetime, savePath)
-	return &Manager{provider: provider, cookieName: cookieName, maxlifetime: maxlifetime, options: options}, nil
+	hashfunc := "sha1"
+	if len(options) > 1 {
+		hashfunc = options[1].(string)
+	}
+	hashkey := "beegosessionkey"
+	if len(options) > 2 {
+		hashkey = options[2].(string)
+	}
+	return &Manager{
+		provider:    provider,
+		cookieName:  cookieName,
+		maxlifetime: maxlifetime,
+		hashfunc:    hashfunc,
+		hashkey:     hashkey,
+		options:     options,
+	}, nil
 }
 
 //get Session
 func (manager *Manager) SessionStart(w http.ResponseWriter, r *http.Request) (session SessionStore) {
 	cookie, err := r.Cookie(manager.cookieName)
+	maxage := -1
+	if len(manager.options) > 3 {
+		switch manager.options[3].(type) {
+		case int:
+			if manager.options[3].(int) > 0 {
+				maxage = manager.options[3].(int)
+			} else if manager.options[3].(int) < 0 {
+				maxage = 0
+			}
+		case int64:
+			if manager.options[3].(int64) > 0 {
+				maxage = int(manager.options[3].(int64))
+			} else if manager.options[3].(int64) < 0 {
+				maxage = 0
+			}
+		case int32:
+			if manager.options[3].(int32) > 0 {
+				maxage = int(manager.options[3].(int32))
+			} else if manager.options[3].(int32) < 0 {
+				maxage = 0
+			}
+		}
+	}
 	if err != nil || cookie.Value == "" {
-		sid := manager.sessionId()
+		sid := manager.sessionId(r)
 		session, _ = manager.provider.SessionRead(sid)
 		secure := false
 		if len(manager.options) > 0 {
 			secure = manager.options[0].(bool)
 		}
-		cookie := http.Cookie{Name: manager.cookieName,
+		cookie = &http.Cookie{Name: manager.cookieName,
 			Value:    url.QueryEscape(sid),
 			Path:     "/",
 			HttpOnly: true,
 			Secure:   secure}
+		if maxage >= 0 {
+			cookie.MaxAge = maxage
+		}
 		//cookie.Expires = time.Now().Add(time.Duration(manager.maxlifetime) * time.Second)
-		http.SetCookie(w, &cookie)
-		r.AddCookie(&cookie)
+		http.SetCookie(w, cookie)
+		r.AddCookie(cookie)
 	} else {
 		//cookie.Expires = time.Now().Add(time.Duration(manager.maxlifetime) * time.Second)
 		cookie.HttpOnly = true
 		cookie.Path = "/"
+		if maxage >= 0 {
+			cookie.MaxAge = maxage
+		}
 		http.SetCookie(w, cookie)
 		sid, _ := url.QueryUnescape(cookie.Value)
 		session, _ = manager.provider.SessionRead(sid)
@@ -103,10 +160,81 @@ func (manager *Manager) GC() {
 	time.AfterFunc(time.Duration(manager.maxlifetime)*time.Second, func() { manager.GC() })
 }
 
-func (manager *Manager) sessionId() string {
+func (manager *Manager) SessionRegenerateId(w http.ResponseWriter, r *http.Request) (session SessionStore) {
+	sid := manager.sessionId(r)
+	cookie, err := r.Cookie(manager.cookieName)
+	if err != nil && cookie.Value == "" {
+		//delete old cookie
+		session, _ = manager.provider.SessionRead(sid)
+		secure := false
+		if len(manager.options) > 0 {
+			secure = manager.options[0].(bool)
+		}
+		cookie = &http.Cookie{Name: manager.cookieName,
+			Value:    url.QueryEscape(sid),
+			Path:     "/",
+			HttpOnly: true,
+			Secure:   secure,
+		}
+	} else {
+		oldsid, _ := url.QueryUnescape(cookie.Value)
+		session, _ = manager.provider.SessionRegenerate(oldsid, sid)
+		cookie.Value = url.QueryEscape(sid)
+		cookie.HttpOnly = true
+		cookie.Path = "/"
+	}
+	maxage := -1
+	if len(manager.options) > 3 {
+		switch manager.options[3].(type) {
+		case int:
+			if manager.options[3].(int) > 0 {
+				maxage = manager.options[3].(int)
+			} else if manager.options[3].(int) < 0 {
+				maxage = 0
+			}
+		case int64:
+			if manager.options[3].(int64) > 0 {
+				maxage = int(manager.options[3].(int64))
+			} else if manager.options[3].(int64) < 0 {
+				maxage = 0
+			}
+		case int32:
+			if manager.options[3].(int32) > 0 {
+				maxage = int(manager.options[3].(int32))
+			} else if manager.options[3].(int32) < 0 {
+				maxage = 0
+			}
+		}
+	}
+	if maxage >= 0 {
+		cookie.MaxAge = maxage
+	}
+	http.SetCookie(w, cookie)
+	r.AddCookie(cookie)
+	return
+}
+
+//remote_addr cruunixnano randdata
+
+func (manager *Manager) sessionId(r *http.Request) (sid string) {
 	b := make([]byte, 24)
 	if _, err := io.ReadFull(rand.Reader, b); err != nil {
 		return ""
 	}
-	return base64.URLEncoding.EncodeToString(b)
+	bs := base64.URLEncoding.EncodeToString(b)
+	sig := fmt.Sprintf("%s%d%s", r.RemoteAddr, time.Now().UnixNano(), bs)
+	if manager.hashfunc == "md5" {
+		h := md5.New()
+		h.Write([]byte(bs))
+		sid = fmt.Sprintf("%s", hex.EncodeToString(h.Sum(nil)))
+	} else if manager.hashfunc == "sha1" {
+		h := hmac.New(sha1.New, []byte(manager.hashkey))
+		fmt.Fprintf(h, "%s", sig)
+		sid = fmt.Sprintf("%s", hex.EncodeToString(h.Sum(nil)))
+	} else {
+		h := hmac.New(sha1.New, []byte(manager.hashkey))
+		fmt.Fprintf(h, "%s", sig)
+		sid = fmt.Sprintf("%s", hex.EncodeToString(h.Sum(nil)))
+	}
+	return
 }