feature(config): allow environment variable override

cmd/server/main.go.gotpl

@@ -76,6 +76,10 @@ func main() {
 
 	}
 
+	if err := config.WithEnvironment(conf); err != nil {
+		log.Fatalf("%+v", errors.Wrap(err, "could not override config with environment"))
+	}
+
 	// Dump configuration if asked
 	if dumpConfig {
 		if err := config.Dump(conf, os.Stdout); err != nil {

internal/config/config.go

@@ -7,11 +7,12 @@ import (
 
 	"github.com/pkg/errors"
 
+	"github.com/caarlos0/env/v6"
 	"gopkg.in/yaml.v2"
 )
 
 type Config struct {
-	Debug bool       `yaml:"debug"`
+	Debug bool       `yaml:"debug" env:"DEBUG"`
 	HTTP  HTTPConfig `yaml:"http"`
 }
 
@@ -32,12 +33,12 @@ func NewFromFile(filepath string) (*Config, error) {
 }
 
 type HTTPConfig struct {
-	Address                 string `yaml:"address"`
-	CookieAuthenticationKey string `yaml:"cookieAuthenticationKey"`
-	CookieEncryptionKey     string `yaml:"cookieEncryptionKey"`
-	CookieMaxAge            int    `yaml:"cookieMaxAge"`
-	TemplateDir             string `yaml:"templateDir"`
-	PublicDir               string `yaml:"publicDir"`
+	Address                 string `yaml:"address" env:"HTTP_ADDRESS"`
+	CookieAuthenticationKey string `yaml:"cookieAuthenticationKey" env:"HTTP_COOKIE_AUTHENTICATION_KEY"`
+	CookieEncryptionKey     string `yaml:"cookieEncryptionKey" env:"HTTP_COOKIE_ENCRYPTION_KEY"`
+	CookieMaxAge            int    `yaml:"cookieMaxAge" env:"HTTP_COOKIE_MAX_AGE"`
+	TemplateDir             string `yaml:"templateDir" env:"HTTP_TEMPLATE_DIR"`
+	PublicDir               string `yaml:"publicDir" env:"HTTP_PUBLIC_DIR"`
 }
 
 func NewDumpDefault() *Config {
@@ -71,3 +72,11 @@ func Dump(config *Config, w io.Writer) error {
 
 	return nil
 }
+
+func WithEnvironment(conf *Config) error {
+	if err := env.Parse(conf); err != nil {
+		return err
+	}
+
+	return nil
+}