Make used of typed atomic.Pointer (#23550)

server/channels/app/platform/web_conn.go

@@ -108,7 +108,7 @@ type WebConn struct {
 	// leave that as an edge-case.
 	reuseCount   int
 	sessionToken atomic.Value
-	session      atomic.Value
+	session      atomic.Pointer[model.Session]
 	connectionID atomic.Value
 	endWritePump chan struct{}
 	pumpFinished chan struct{}
@@ -304,7 +304,7 @@ func areAllInactive(conns []*WebConn) bool {
 
 // GetSession returns the session of the connection.
 func (wc *WebConn) GetSession() *model.Session {
-	return wc.session.Load().(*model.Session)
+	return wc.session.Load()
 }
 
 // SetSession sets the session of the connection.