config

README

config

This is a very minimal utility for reading configuration values from either command-line flags, environment variables, or configuration files.

This library does not use flag package for parsing flags

Quick Start

package main

import (
  "fmt"
  "github.com/moorara/goto/config"
)

type Spec struct {
  Enabled bool
  ServiceName string
  ServicePort int
  LogLevel string
}

func main() {
  spec := Spec{}
  config.Pick(&spec)
  fmt.Printf("%+v\n", spec)
}

The precendence of sources for values is as follows:

1. command-line flags
2. environment variables
3. configuration files
4. default values (set when creating spec)

You can pass the configuration values using flags using any of the syntaxes below:

main -enabled  -service.name=users -service.port=8080 -log.level=info
main --enabled  --service.name=users --service.port=8080 --log.level=info
main -enabled  -service.name users -service.port 8080 -log.level info
main --enabled  --service.name users --service.port 8080 --log.level info

You can pass the configuration values using environment variables as follows:

export ENABLED=true
export SERVICE_NAME=users
export SERVICE_PORT=8080
export LOG_LEVEL=info

You can also write the configuration values in files and set the paths to the files using environment variables:

export ENABLED_FILE=...
export SERVICE_NAME_FILE=...
export SERVICE_PORT_FILE=...
export LOG_LEVEL_FILE=...

Complete Example

package main

import (
  "fmt"
  "github.com/moorara/goto/config"
)

type Spec struct {
	field        string   // Unexported, will be skipped
	FieldString  string   `flag:"fieldString" env:"CONFIG_FIELD_STRING" file:"CONFIG_FILE_FIELD_STRING"`
	FieldBool    bool     `flag:"fieldBool" env:"CONFIG_FIELD_BOOL" file:"CONFIG_FILE_FIELD_BOOL"`
	FieldFloat32 float32  `flag:"fieldFloat32" env:"CONFIG_FIELD_FLOAT32" file:"CONFIG_FILE_FIELD_FLOAT32"`
	FieldFloat64 float64  `flag:"fieldFloat64" env:"CONFIG_FIELD_FLOAT64" file:"CONFIG_FILE_FIELD_FLOAT64"`
	FieldInt     int      `flag:"fieldInt" env:"CONFIG_FIELD_INT" file:"CONFIG_FILE_FIELD_INT"`
	FieldInt8    int8     `flag:"fieldInt8" env:"CONFIG_FIELD_INT8" file:"CONFIG_FILE_FIELD_INT8"`
	FieldInt16   int16    `flag:"fieldInt16" env:"CONFIG_FIELD_INT16" file:"CONFIG_FILE_FIELD_INT16"`
	FieldInt32   int32    `flag:"fieldInt32" env:"CONFIG_FIELD_INT32" file:"CONFIG_FILE_FIELD_INT32"`
	FieldInt64   int64    `flag:"fieldInt64" env:"CONFIG_FIELD_INT64" file:"CONFIG_FILE_FIELD_INT64"`
	FieldUint    uint     `flag:"fieldUint" env:"CONFIG_FIELD_UINT" file:"CONFIG_FILE_FIELD_UINT"`
	FieldUint8   uint8    `flag:"fieldUint8" env:"CONFIG_FIELD_UINT8" file:"CONFIG_FILE_FIELD_UINT8"`
	FieldUint16  uint16   `flag:"fieldUint16" env:"CONFIG_FIELD_UINT16" file:"CONFIG_FILE_FIELD_UINT16"`
	FieldUint32  uint32   `flag:"fieldUint32" env:"CONFIG_FIELD_UINT32" file:"CONFIG_FILE_FIELD_UINT32"`
	FieldUint64  uint64   `flag:"fieldUint64" env:"CONFIG_FIELD_UINT64" file:"CONFIG_FILE_FIELD_UINT64"`
}

func main() {
  spec := Spec{
    FieldString: "default value",
  }
  config.Pick(&spec)
  fmt.Printf("%+v\n", spec)
}

Documentation

Index

• func Pick(spec interface{}) error

Functions

func Pick

func Pick(spec interface{}) error

Pick reads values for a struct of specifications