Instead of logging an error, check if a property is empty before attempting to
call strconv.ParseFloat on it.
ERRO[0005] error parsing interface metric value device=gw error="strconv.ParseFloat: parsing \"\": invalid syntax" interface=ether2 property=tx-drop value=
* added config file implementation, refactoring
* add gitignore
* improved test
* preperations for more metrics
* added resource metrics
* added first bgp metrics
* added asn as label for bgp metrics
* added prefix and message counts to bgp metrics
* simplified
* Update README.md
* added yaml dependency
* fixed go routine call
* added timeout
* clean up
* added TLS support
* set default api port for TLS
* added routes metric
* added missing log information
* added type collectorContext to reduce the count of parameters for better readability
* added DHCP and DHCPv6 metrics
* filter for active dhcp leases only
* added pool metrics
* enable/disable feature in config file
* refactoring
* clean up
* comment fix
