All Unix machines have a separate server process that is responsible for receiving logging data and writing it to log files. Various log servers exist that work on Unix machines; however, only two of them are used on most Unix variants: syslogd(8) and rsyslogd(8).

On macOS machines, the name of the process is syslogd(8). On the other hard, most Linux machines use rsyslogd(8), which is an improved and more reliable version of syslogd(8), which was the original Unix system utility for message logging.

However, despite the Unix variant you are using or the name of the server process used for logging, logging works the same way on every Unix machine and therefore does not affect the Go code that you will write.

The configuration file of rsyslogd(8) is usually named rsyslog.conf and is located in /etc. The contents of a rsyslog.conf configuration file, without the lines with comments and lines starting with $, might look like the following:

$ grep -v '^#' /etc/rsyslog.conf | grep -v '^$' | grep -v '^$'
auth,authpriv.*                /var/log/auth.log
*.*;auth,authpriv.none        -/var/log/syslog
daemon.*                      -/var/log/daemon.log
kern.*                        -/var/log/kern.log
lpr.*                         -/var/log/lpr.log
mail.*                        -/var/log/mail.log
user.*                        -/var/log/user.log
mail.info                     -/var/log/mail.info
mail.warn                     -/var/log/mail.warn
mail.err                       /var/log/mail.err
news.crit                      /var/log/news/news.crit
news.err                       /var/log/news/news.err
news.notice                   -/var/log/news/news.notice
*.=debug;
    auth,authpriv.none;
    news.none;mail.none       -/var/log/debug
*.=info;*.=notice;*.=warn;
    auth,authpriv.none;
    cron,daemon.none;
    mail,news.none        -/var/log/messages
*.emerg                :omusrmsg:*
daemon.*;mail.*;
    news.err;
    *.=debug;*.=info;
    *.=notice;*.=warn    |/dev/xconsole
local7.* /var/log/cisco.log

In order to send your logging information to /var/log/cisco.log, you will need to use the local7 logging facility. The star character after the name of the facility tells the logging server to catch every logging level that goes to the local7 logging facility and write it to /var/log/cisco.log.

The syslogd(8) server has a pretty similar configuration file that is usually /etc/syslog.conf. On macOS High Sierra, the /etc/syslog.conf file is almost empty and has been replaced by /etc/asl.conf. Nevertheless, the logic behind the configuration of /etc/syslog.conf, /etc/rsyslog.conf, and /etc/asl.conf is the same.