Forti Switch Ring Topology

You essentially would have a chain with traffic from switch 8 having to traverse all the way to switch1 to get to the fortigate. If a link in the chain is broken, everything without a path to the Fortigate on the active link will loose this funtionality.

as I read from Fortinet, they give us un recommended solution which is set Forti switches ports as a Hardware switch then apply them on Forti Link mode 

Are there any alternative solutions than this mentioned Please advice

Please refer this: https://docs.fortinet.com/document/fortiswitch/7.6.1/fortilink-guide/617516/determining-the-network-topology