[MM-52550] platform/web_conn: fix a possible data race issue (#23255)

* platform/web_conn: fix a possible data race issue

* reflect review comments

---------

Co-authored-by: Ibrahim Serdar Acikgoz <ibrahim@ibrahims-mac.local>
Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/platform/web_hub.go

@@ -436,8 +436,9 @@ func (h *Hub) Start() {
 
 				conns := connIndex.ForUser(webConn.UserId)
 				if len(conns) == 0 || areAllInactive(conns) {
+					userID := webConn.UserId
 					h.platform.Go(func() {
-						h.platform.SetStatusOffline(webConn.UserId, false)
+						h.platform.SetStatusOffline(userID, false)
 					})
 					continue
 				}
@@ -452,8 +453,9 @@ func (h *Hub) Start() {
 				}
 
 				if h.platform.isUserAway(latestActivity) {
+					userID := webConn.UserId
 					h.platform.Go(func() {
-						h.platform.SetStatusLastActivityAt(webConn.UserId, latestActivity)
+						h.platform.SetStatusLastActivityAt(userID, latestActivity)
 					})
 				}
 			case userID := <-h.invalidateUser: