Verify syslog is running or else enable it.
$ ps -aux | grep syslog
root 11703 0.0 0.4 14424 1992 - IsJ 9:17AM 0:00.01 /usr/sbin/syslogd -ss
Now verify syslog is running in the expected local address. The log/syslog package looks for syslog in /var/run/syslog or /dev/log. If it does not find it there, you see the "Unix syslog delivery error" as per http://golang.org/src/pkg/log/syslog/syslog_unix.go.
To find the local address of syslog use the sockstat command
$sockstat
USER COMMAND PID FD PROTO LOCAL ADDRESS FOREIGN ADDRESS
root login 12104 3 dgram -> /var/run/logpriv
root login 11791 3 dgram -> /var/run/logpriv
root cron 11754 4 dgram -> /var/run/logpriv
root syslogd 11703 4 dgram /var/run/log
root syslogd 11703 5 dgram /var/run/logpriv
In above case, syslog is running at /var/run/log. So, I created a symlink from /var/run/log to /var/log/syslog and the error goes away.
$ln -sf /var/run/log /var/run/syslog