generating secret for mtproto faces:unknown flag -c, did you mean one of “-h”, “-v”, “-x”?

Solution for generating secret for mtproto faces:unknown flag -c, did you mean one of “-h”, “-v”, “-x”?
is Given Below:

I want to generate secret for telegram messenger in ubuntu20 server via mtg

with the command:

mtg generate-secret -c host.example.com tls

but I get this error:

[email protected]:/home/ubuntu/mtg# mtg generate-secret -c example.com tls
mtg: error: unknown flag -c, did you mean one of “-h”, “-v”, “-x”?”

what should I do??