About envcfg

envcfg is a package to retrieve configuration settings from the environment, in adherence with 12-factor app principles.

Installing

Install in the usual Go fashion:

$ go get -u github.com/kenshaw/envcfg

Using

envcfg can be used similarly to the following:

// examples/main.go
package main

import (
	"fmt"
	"log"
	"net/http"

	"github.com/kenshaw/envcfg"
)

func main() {
	// load config from the default APP_CONFIG environment variable
	config, err := envcfg.New()
	if err != nil {
		log.Fatal(err)
	}

	// load additional config from SOME_OTHER_VAR environment variable
	config2, err := envcfg.New(
		envcfg.VarName("SOME_OTHER_VAR"),
	)
	if err != nil {
		log.Fatal(err)
	}
	config2 = config2

	// read a config key
	val := config.GetKey("mysection.mykeyname")
	log.Printf("> val: %s", val)

	// create a http.Server with a host, port, and TLS based on config pulled
	// from environment
	s := &http.Server{
		Addr:      fmt.Sprintf("%s:%d", config.Host(), config.Port()),
		TLSConfig: config.TLS(nil),
	}
	log.Fatal(s.ListenAndServe())
}

Please see the GoDoc listing for a full API listing.

Environment Variables

By default, envcfg loads configuration data from the base64-encoded environment variable APP_CONFIG, and expects a git config style configuration file of sections, subsections, and keys.

Config files and key data

Configuration data is stored in git config style configuration files, and uses the github.com/kenshaw/ini package for parsing configuration data.

The below is the examples/sample.config:

# examples/sample.config
[runtime]
environment="$ENV||production"                   ; production / development / etc.

[server]
host="$HOST||example.com"                        ; hostname
port="$PORT||8443"                               ; port
certs="$CERTS||./env/certs"                      ; certificate directory cache
certProvider="dns:godo:<domain>:<email>:<token>" ; certificate provider

[google]
creds="$GOOGLECREDS||env/gsa.json||file"         ; "file" encoded gsa credentials loaded from disk,
                                                 ; relative to the current working directory

[service "something"]
key="$NAME||subdir/myfile||relfile"              ; "relfile" encoded file will be loaded relative to the original config file
                                                 ; for example, if the config file was on disk at /etc/myapp then
                                                 ; the /etc/myapp/subdir/myfile value would be loaded

[example]
b64value="$B64VALUE||e30K||base64"               ; "base64" encoded value

Certificate Providers

The following certificate providers are supported for server.certProvider:

Name	Type	Example
auto	LetsEncrypt TLS-SNI-01	auto
disk	Certificate on disk	disk:/path/to/cert.pem:/path/to/key.pem
dns	LetsEncrypt DNS-01	dns:clouddns:mydomain.com:ken@example.com:my-managed-zone-name:/path/to/credentials.json

LetsEncrypt DNS-01 Provider

DNS certificate provider strings have a general form of dns:<type>:<domain>:<email>:....

Type	DNS Provider	Parameters
godo	DigitalOcean DNS	<type>:<domain>:<email>:<token>
clouddns	Google Cloud DNS	<type>:<domain>:<email>:<managed-zone-name>:/path/to/credentials.json