After installing Mojave I was prompted in Terminal and FileZilla for a password whenever I connected to my web server. Since I use key files to connect I thought this behavior was odd. This appears to be a MacOS issue as Apple has changed the behavior in Sierra.
I solved it by creating the following file (or editing it if you already have one):
~/.ssh/config
Add the following:
Host *
UseKeychain yes
AddKeysToAgent yes
ForwardAgent yes
IdentityFile ~/.ssh/id_rsa
Once that was done I did the following in Terminal:
ssh-add-K ~/.ssh/id_rsa
That’s it. Now my apps no longer prompt me for a password every time I try to use my ssh keys.