a config file or env vars
some json or yaml file - possibly stored in a db
some of these i had control over - others could be modified by a user in an app that i do not necessarily must have access to to employ validation or control the way things are stored

I also needed:

default values, "NOT NULL" like constraints, and validation that involves dependencies between different config values
the ability to reload the configs from all its sources in its original order in an easy way

Features

Usage

Cfg := struct {
	Config

	BoolSetting   bool    `default:"true"`
	StringSetting string  `default:"foo" json:"string_setting"`
	IntSetting    int     `required:"false" default:"23" should:"BeGreaterThanOrEqualTo_FloatSetting"`
	FloatSetting  float64 `default:"1.681"`

	SingleValueConfig struct {
		StringSetting string  `default:"bar" json:"single_value_config__string_setting"`
		IntSetting    int     `required:"false" default:"42" should:"BeGreaterThanOrEqualTo_.FloatSetting"`
		FloatSetting  float64 `should:"BeLessThanOrEqualTo_IntSetting"`
	}

	SliceConfig struct {
		StringSliceSetting []string  `default:"foo,bar"`
		IntSliceSetting    []int     `default:"23,42"`
		FloatSliceSetting  []float64 `default:"1.394,1.112"`
	}

	NestedValueConfig struct {
		StringSetting          string `default:"NestedOuterFoo"`
		InnerNestedValueConfig struct {
			StringSetting string `default:"NestedInnerFoo"`
		}
	}

	StringSet *set.StringSet `alias:someNameICantControl`
	IntSet    *set.IntSet
}{}

err = cobj.InitConfig(&Cfg, []cobj.InitFunc{
	cobj.InitFunc{
		F:           loadConfFile,
		ExitOnError: true,
	},
	cobj.InitFunc{
		F:           setupThisOtherThing,
		ExitOnError: false,
	},
}...)


func loadConfFile() (err error) {
	conf := make(map[string]string)

    ...

	err = Cfg.Set(conf)
	return
}