NO_PUBKEY

[Peekaboo1]

"https://apt.hrfee.dev trusty InRelease: The following signatures couldn't be verified because the public key is not available"

"The repository 'https://apt.hrfee.dev trusty InRelease' is not signed"

[hrfee]

Have you added the GPG key? You'll need to run this:

sudo apt-get update
sudo apt-get install curl apt-transport-https gnupg
curl https://apt.hrfee.dev/hrfee.pubkey.gpg | sudo apt-key add -

Then apt-get update and you should be able to install jfa-go.