peg

super simple app config library that uses struct-tags for declaration

learn by example

type AppConfig struct {
    Server Server `peg.name:"server"`
    DB     DB     `peg.name:"db"`
}

type Server struct {
    BindAddr string `peg.name:"bind-addr" peg.usage:"network address to listen to" peg.default:":8080"`
    TLS      string `peg.name:"tls"`
}

type DB struct {
    Host string `peg.name:"host" peg.usage:"hostname of the db"`
    Port int    `peg.name:"port" peg.usage:"port of the db" peg.default:"5432"`
    User string `peg.name:"user" peg.usage:"user of the db" peg.default:"user1"`
    Pass string `peg.name:"pass" peg.usage:"password of the db"`
}

type TLS struct {
    Enabled bool   `peg.name:"enabled" peg.usage:"weather to enable tls on the server" peg.default:"false"`
    Cert    string `peg.name:"cert" peg.usage:"path to the tls cert file"`
    Key     string `peg.name:"key" peg.usage:"path to the tls key file"` 
}

func func main() {
    var conf AppConfig
    peg.Bind(&conf).Read()

    // if app did run with -server.tls.enabled or env var SERVER_TLS_ENABLED=true
    if conf.TLS.Enabled {
        ...
    }
}

tag names:

config fields are defined using the following tags:

peg.name
the name of the config field

peg.usage
usage to print in the help section

peg.default
default value of the field

sources:

config field values are read from the following sources. the key of the field is composed of the full path of the field name according to the conventions of the source.

flags

read values from the program arguments.
in the above example, the flag name for whether to enable tls or not is -server.tls.enabled

env vars

read values from environment variables or from .env file in the working dir.
in the above example, the env var name for whether to enable tls or not is SERVER_TLS_ENABLED