Declarative way to describe an application's config

[alldroll]

The only way to get know about the application's config variables is to look at main.go.

> GRPC_API_PORT=test ENABLE_ENCRYPTION=test scripts/./dev

panic: strconv.ParseBool: parsing "test": invalid syntax

goroutine 1 [running]:
main.mustBool(...)
	/home/alldroll/work/kgs/main.go:88
main.main()
	/home/alldroll/work/kgs/main.go:27 +0xc25
exit status 2

I see several problems here

• The reported error forces a developer to look at the code line in order to understand what kind of application's config variable is invalid.
• It is difficult to understand which variables are required, which are optional.

As a solution, we can try to use a struct and the corresponding struct tags

[magicoder10]

This is now provided by the app framework: https://github.com/short-d/app/blob/master/fw/envconfig/envconfig.go. Need to upgrade kgs to use it.