replace ioutil with io package and other minor improvements

sessions/database.go

@@ -94,24 +94,28 @@ func (s *mem) OnUpdateExpiration(string, time.Duration) error { return nil }
 // immutable depends on the store, it may not implement it at all.
 func (s *mem) Set(sid string, key string, value interface{}, _ time.Duration, immutable bool) error {
 	s.mu.RLock()
-	s.values[sid].Save(key, value, immutable)
+	store, ok := s.values[sid]
 	s.mu.RUnlock()
+	if ok {
+		store.Save(key, value, immutable)
+	}
 
 	return nil
 }
 
 func (s *mem) Get(sid string, key string) interface{} {
 	s.mu.RLock()
-	v := s.values[sid].Get(key)
+	store, ok := s.values[sid]
 	s.mu.RUnlock()
+	if ok {
+		return store.Get(key)
+	}
 
-	return v
+	return nil
 }
 
 func (s *mem) Decode(sid string, key string, outPtr interface{}) error {
-	s.mu.RLock()
-	v := s.values[sid].Get(key)
-	s.mu.RUnlock()
+	v := s.Get(sid, key)
 	if v != nil {
 		reflect.ValueOf(outPtr).Set(reflect.ValueOf(v))
 	}
@@ -119,29 +123,45 @@ func (s *mem) Decode(sid string, key string, outPtr interface{}) error {
 }
 
 func (s *mem) Visit(sid string, cb func(key string, value interface{})) error {
-	s.values[sid].Visit(cb)
+	s.mu.RLock()
+	store, ok := s.values[sid]
+	s.mu.RUnlock()
+	if ok {
+		store.Visit(cb)
+	}
+
 	return nil
 }
 
 func (s *mem) Len(sid string) int {
 	s.mu.RLock()
-	n := s.values[sid].Len()
+	store, ok := s.values[sid]
 	s.mu.RUnlock()
+	if ok {
+		return store.Len()
+	}
 
-	return n
+	return 0
 }
 
 func (s *mem) Delete(sid string, key string) (deleted bool) {
 	s.mu.RLock()
-	deleted = s.values[sid].Remove(key)
+	store, ok := s.values[sid]
 	s.mu.RUnlock()
+	if ok {
+		deleted = store.Remove(key)
+	}
+
 	return
 }
 
 func (s *mem) Clear(sid string) error {
-	s.mu.Lock()
-	s.values[sid].Reset()
-	s.mu.Unlock()
+	s.mu.RLock()
+	store, ok := s.values[sid]
+	s.mu.RUnlock()
+	if ok {
+		store.Reset()
+	}
 
 	return nil
 }
@@ -150,7 +170,6 @@ func (s *mem) Release(sid string) error {
 	s.mu.Lock()
 	delete(s.values, sid)
 	s.mu.Unlock()
-
 	return nil
 }