git push -u origin master Agent admitted failure to sign using the key. Permission denied (publickey). fatal: The remote end hung up unexpectedly
If you got error like that, you can use command
ssh-add ~/.ssh/id_rsa to solve.
If you just generated a key, ssh-agent does not know about it so it can't sign using the key - exactly what the error message says.
To add the key, you either need to restart ssh-agent (i.e. log out and log back in) or to use ssh-add to re-scan the keys.