MacOS ssh keyring
From IIHE Wiki
If you used to not type your passphrase when using ssh and this functionality is not working anymore since you've updated your Mac? This is a known issue since MacOS changed the way ssh keys are managed in Sierra ([reference|https://developer.apple.com/library/content/technotes/tn2449/_index.html#//apple_ref/doc/uid/DTS40017589]).
The following post explain simply how to get it working as before: http://joshbuchea.com/revert-ssh-agent-behavior-pre-macos-sierra/