autoconfig

README

Golang auto-config library

This library populates environment variables a structure without having to repeat boilerplate code.

Details

When creating a struct, add the tags below to read the environment variables and populate the struct values. Default values can also be specified if no values are found. There are 2 tags that MUST exist for auto-populating are config and mapstructure. The mapstructure tag is used by Viper itself to populate the values read from the environment variable name whereas the config tag sets the rules for the values.

The name in the mapstructure tag represents the environment variable name to be read.

The possible parameters for the config config tag are

name	description
default	default value to use if no environment variable value exists.
required	an environment variable value MUST be provided.
struct	if the variable type is a struct, use this tag, which allows it to delve into to populate the fields.

Example

const (
	// EnvPrefix - environment variable prefix
	EnvPrefix = "TRAEFIK_ADGUARDHOME"
)

// AppConfig - application configuration from config file or environment variables
type AppConfig struct {

		Logger struct {
			Format      string `yaml:"format" json:"format" mapstructure:"LOGGER_FORMAT" config:"default=kv"`                    // 'kv' or 'json'
			MinLevel    string `yaml:"minLevel" json:"minLevel" mapstructure:"LOGGER_MIN_LEVEL" config:"default=info"`           // minimum level of logging - supported values are 'debug', 'info', 'warn', 'error'
			Output      string `yaml:"output" json:"output" mapstructure:"LOGGER_OUTPUT" config:"default=stdout"`                // output for logging - 'stdout' or 'file'
			Destination string `yaml:"destination" json:"destination" mapstructure:"LOGGER_DESTINATION" config:"default=stdout"` // destination for logging, only for 'file'		
            handler  *slog.Logger
		} `yaml:"logger" json:"logger" config:"struct"`


	ServerIP string `yaml:"server_ip" json:"server_ip" mapstructure:"SERVER_IP" config:"required"`

	Docker struct {
		Address string `yaml:"value" json:"value" mapstructure:"DOCKER_ADDRESS" config:"default=unix:///var/run/docker.sock"`
	} `yaml:"docker" json:"docker" config:"struct"`

	AdguardHome struct {
		Address  string `yaml:"address" json:"address" mapstructure:"ADDRESS" config:"required"`
		Username string `yaml:"value" json:"value" mapstructure:"USERNAME" config:"required"`
		Password string `yaml:"file" json:"file" mapstructure:"PASSWORD" config:"required"`
	} `yaml:"adguardhome" json:"adguardhome" config:"struct"`
}

func (appConfig *AppConfig) String() (str string) {
	bytes, _ := json.Marshal(appConfig)
	return string(bytes)
}

// Setup - set values for fields that depend on other values
func (appConfig *AppConfig) Setup() (err error) {
    // do any custom checks
	return
}

cfg := autoconfig.New(EnvPrefix) // create a new instance of `autoconfig` and pass the base environment variable for `Viper`. This helps distinguish variable names for specific applications
appConfig = new(AppConfig) // create new instance of `AppConfig`

err := cfg.ReadEnv(appConfig) // read the environment variables and populates the given structure
cobra.CheckErr(err) // check for any error that occured

err = cfg.Check(appConfig) // check the rules specified in the `config` tag
cobra.CheckErr(err) // check for any error that occured

err = appConfig.Setup() // run any custom checks
cobra.CheckErr(err) // check for any error that occured

Documentation

Index

• type Config
  • func New(prefix string) *Config
  • func (c *Config) Check(s any) error
  • func (c *Config) Create(project, baseCfgName, baseDirname string, cfgType ConfigType) error
  • func (c *Config) ReadEnv(s any) error
  • func (c *Config) ReadFile(s any) error
• type ConfigType
  • func (ct ConfigType) IsValid() (valid bool)
  • func (ct ConfigType) String() (str string)

Types

type Config

type Config struct {
	// contains filtered or unexported fields
}

func New

func New(prefix string) *Config

New creates a new Config, setting up maps & env prefix.

func (*Config) Check

func (c *Config) Check(s any) error

Check validates “required” fields and applies “default=” defaults. It recurses into nested structs when tagConfig:"struct" is present. Uses cached fieldMeta for speed. `s` must be pointer to struct.

func (*Config) Create

func (c *Config) Create(
	project, baseCfgName, baseDirname string,
	cfgType ConfigType,
) error

Create sets up config directory & viper file settings.

func (*Config) ReadEnv

func (c *Config) ReadEnv(s any) error

ReadEnv binds environment variables using each field’s `mapstructure` tag and then unmarshals into `s`. It also records `msTag` for later validation.

func (*Config) ReadFile

func (c *Config) ReadFile(s any) error

ReadFile instructs viper to read a config file and unmarshal into `s`. `s` must be a pointer to a struct.

type ConfigType

type ConfigType uint8

const (
	ConfigTypeNone ConfigType = iota
	ConfigTypeYAML
	ConfigTypeJSON
)

func (ConfigType) IsValid

func (ct ConfigType) IsValid() (valid bool)

func (ConfigType) String

func (ct ConfigType) String() (str string)