github.com/knadh/koanf (go): Simple, lightweight, extensible, configuration management library for Go. Support for JSON, TOML, YAML, env, command line, file, S3 etc. Alternative to viper.
Keywords: config|config-loader|configuration|configuration-file|configuration-management|etcd-client|go|golang|golang-package|s3-bucket|toml|viper|yaml