how to pass content of file variable in fish shell

I want to use the .pem for secure ssh connection so how can I pass the content of the pem to a variable in fish script?

set key /Users/mesutgunes/project/mproject-key.pem
ssh -i (cat $key) labs[1] ???

Solution

Set environment value.

set file /Users/mesutgunes/project/mproject-key.pem
ssh -i $file host

regards