[CentOS] if no NFS server clients are waiting..

What can I do, If the NFS server is rebooting/offline?
I mean the clients just wait and wait and wait...

I tried to set

timeo=5,retrans=2

mount options when mounting nfs in fstab on client side =
still no luck, clients are just waiting...
Can I set a timeout somewhere? :D

Thank you for any tips
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