Update slack info

README.md

@@ -43,7 +43,7 @@ BFE is a modern layer 7 load balancer from baidu.
 - Contributors: [CONTRIBUTORS](CONTRIBUTORS.md)
 
 ## Communication
-- BFE community on Slack: [Sign up](https://join.slack.com/t/bfe-networks/shared_invite/zt-cn04xsqr-j7LDFmPkCuCZ39OLcHlMBA) and join channels on topics that interest you.
+- BFE community on Slack: [Sign up](https://slack.cncf.io/) CNCF Slack and join bfe channel.
 - BFE developer group on WeChat: [Send a request mail](mailto:yangsijie@baidu.com) with your WeChat ID and a contribution you've made to BFE(such as a PR/Issue). We will invite you right away.
 
 ## License

docs/en_us/COMMUNITY.md

@@ -2,7 +2,9 @@ We are very interested in building a community around BFE. If you are interested
 
 ## COMMUNITY 
 
-**BFE community on Slack**: [Sign up](https://join.slack.com/t/bfe-networks/shared_invite/zt-cn04xsqr-j7LDFmPkCuCZ39OLcHlMBA) and join channels on topics that interest you.
+**BFE user forum**: [Github Discussions](https://github.com/bfenetworks/bfe/discussions).
+
+**BFE community on Slack**: [Sign up](https://slack.cncf.io/) CNCF Slack and join bfe channel.
 
 **WeChat developer group**: [Send a request mail](mailto:bfe-osc@baidu.com) with your WeChat ID and a contribution you have made to BFE(such as a PR/Issue). We will invite you right away.
 

docs/zh_cn/COMMUNITY.md

@@ -2,10 +2,12 @@
 
 ## BFE社区
 
-**BFE Slack社区**: [登陆](https://join.slack.com/t/bfe-networks/shared_invite/zt-cn04xsqr-j7LDFmPkCuCZ39OLcHlMBA)并关注你感兴趣的话题。
+**BFE用户论坛**: 前往[Github Discussions](https://github.com/bfenetworks/bfe/discussions)讨论。
 
 **BFE开发者微信群**: [发送申请邮件](mailto:bfe-osc@baidu.com)并注明您的微信账号及贡献(例如提交的PR/Issue链接)，我们将立即邀请您加入。
 
+**BFE Slack社区**: [登陆](https://slack.cncf.io/)CNCF Slack并关注bfe频道。
+
 **Twitter**: [@BFE-Networks](https://twitter.com/BfeNetworks)
 
 **Issue tracker**: 在[GitHub issue tracker](https://github.com/bfenetworks/bfe/issues) 反馈bug或功能需求。