Add TLS authentication using official exporter-toolkit

[tuannh99]

This enables TLS support for consul_exporter, using the official exporter-toolkit

level=info ts=2021-06-05T11:39:53.390Z caller=main.go:323 msg="Starting collectd_exporter" version="(version=0.5.0, branch=add-tls-authentication, revision=c541af78b805095c2e3ba6d989d525d34cc916ac)"
level=info ts=2021-06-05T11:39:53.390Z caller=main.go:324 msg="Build context" context="(go=go1.16.3, user=mymachine, date=20210605-11:38:38)"
level=info ts=2021-06-05T11:39:53.390Z caller=main.go:346 msg="Listening on address" address=:9103
level=info ts=2021-06-05T11:39:53.393Z caller=tls_config.go:224 msg="TLS is enabled." http2=true

CC @juliusv

[juliusv]

👍 Thanks, looks good to me at a first glance! @roidelapluie to you too (as the exporter toolkit person)?

[roidelapluie]

Does collectd support TLS? (I am asking because I know it does not accept TLS inboud last time I checked)

[juliusv]

I'm not sure, as I've never dealt with collectd for real and only became the maintainer of this exporter by historical accident :) I do see some TLS options on https://collectd.org/documentation/manpages/collectd.conf.5.shtml, but not 100% if those are what you'd be looking for.

But in any case, will merge, thanks for checking as well!