Using linux environment variable in rsyslog template

i was able to use this guidance rsyslog: Specify `action` parameters from environment variables

to shell out from the config file to get the environment variables in the template:

template(name="logfile" type="list") {
   constant(value="{")

   constant(value="\"@timestamp\":\"")     
   property(name="timegenerated" dateFormat="rfc3339")
   constant(value="\", ")
   
   constant(value="\"pod_namespace\":\"")     
   constant(value=`echo $KUB_POD_NAMESPACE`)
   constant(value="\", ")
   
   constant(value="\"pod_name\":\"")     
   constant(value=`echo $KUB_POD_NAME`)
   constant(value="\", ")
   
   constant(value="\"pod_ip\":\"")     
   constant(value=`echo $KUB_INSTANCE_ADDR`)
   constant(value="\", ")
   
   property(name="$!all-json" position.from="2")
}