feat(config): support load env variables as config (#564)

internal/config/base.go

@@ -11,6 +11,7 @@ import (
 	"github.com/ArtalkJS/Artalk/internal/utils"
 	"github.com/knadh/koanf"
 	"github.com/knadh/koanf/parsers/yaml"
+	"github.com/knadh/koanf/providers/env"
 	"github.com/knadh/koanf/providers/file"
 )
 
@@ -29,6 +30,18 @@ func NewFromFile(cfgFile string) (*Config, error) {
 		return nil, fmt.Errorf("config file read error: %w", err)
 	}
 
+	// load environment variables and merge into the loaded config
+	const envPrefix = "ATK_"
+	if err := kf.Load(env.Provider(envPrefix, ".", func(s string) string {
+		// FOO__BAR -> foo_bar to handle dash in config names
+		s = strings.ToLower(strings.TrimPrefix(s, envPrefix))
+		s = strings.ReplaceAll(s, "__", "-")
+		s = strings.ReplaceAll(s, "_", ".")
+		return strings.ReplaceAll(s, "-", "_")
+	}), nil); err != nil {
+		return nil, fmt.Errorf("config environment variable parse error: %w", err)
+	}
+
 	// create new config instance
 	conf := &Config{
 		cfgFile: cfgFile,