Change default host to empty string

[timtorChen]

After upgrade from v0.3.1 to v0.4.0, I found kromgo is not be able to access form the nginx.
It seems the default value separated after summer cleaning cuase the issue.

kromgo/cmd/kromgo/init/configuration/configuration.go

Lines 14 to 18 in eb63020

	ServerHost string `env:"SERVER_HOST" envDefault:"localhost"`
	ServerPort int `env:"SERVER_PORT" envDefault:"8080"`
	HealthHost string `env:"HEALTH_HOST" envDefault:"localhost"`
	HealthPort int `env:"HEALTH_PORT" envDefault:"8888"`

It would be more suitable for a default use case by changing default ServerHost to an empty string "" or "0.0.0.0".

[kashalls]

Sorry, this one got lost in my box somehow...

I can default this to be "0.0.0.0" which makes more sense. The issue with the health server though is that you don't particularly want to expose this, so this might stay as localhost. and can be configured if needed.

[timtorChen]

Never mind, thank for your awesome project.

Hmm, I have a different point of view. As the health server is designed for Prometheus to scrape, and Prometheus is typically an external server to Kromgo. Thus, I think it might make sense for the HealthHost to also default to 0.0.0.0.