Add log-format option

config.yaml.example

@@ -8,6 +8,7 @@
 #idle-timeout: 300
 #active-timeout: 10
 #log-file: /var/log/pgterminate/pgterminate.log
+#log-format: 'pid=%p user=%u db=%d client=%r state=%s state_duration=%m query=%q'
 #pid-file: /var/run/pgterminate/pgterminate.pid
 #log-destination: console|file|syslog
 #syslog-ident: pgterminate
@@ -20,4 +21,4 @@
 #    user1
 #    user2
 #exclude-users-regex: "(user1|user2)"
-#cancel
+#cancel