15249 sync.pool (#16103)

* use sync.pool for session

* added back to sync pool

* reverted change

* added a new line

* added back session object

* added back session object

* added back session object

* revert

* refactored into function

* added the session object back into the pool

* work in progress

* work in progress

* work in progress

* code review comments

Co-authored-by: Arjuna Marambe <arjunam@buildxact.com>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/plugin_requests.go

@@ -130,6 +130,8 @@ func (a *App) servePluginRequest(w http.ResponseWriter, r *http.Request, handler
 	r.Header.Del("Mattermost-User-Id")
 	if token != "" {
 		session, err := a.GetSession(token)
+		defer ReturnSessionToPool(session)
+
 		csrfCheckPassed := false
 
 		if err == nil && cookieAuth && r.Method != "GET" {
@@ -180,7 +182,7 @@ func (a *App) servePluginRequest(w http.ResponseWriter, r *http.Request, handler
 			csrfCheckPassed = true
 		}
 
-		if session != nil && err == nil && csrfCheckPassed {
+		if (session != nil && session.Id != "") && err == nil && csrfCheckPassed {
 			r.Header.Set("Mattermost-User-Id", session.UserId)
 			context.SessionId = session.Id
 		}