Configuration helper for mapping environment vars to a config struct
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README.md

envconfig

Package envconfig provides a function called Unmarshal that allows you to dump environment variable values into a structure using struct tags

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Installing

You can install the package using the go get command:

go get -u github.com/everettcaleb/envconfig

Usage Example

For an environment where PORT, DB_CONNECTION, and REDIS_HOST are defined and we want to require that a database connection string and Redis host are provided:

package main

import (
    "fmt"

    "github.com/everettcaleb/envconfig"
)

type appSettings struct {
    Port         int    `env:"PORT"`
    DBConnection string `env:"DB_CONNECTION" required:"true"`
    Redis        redisSettings
}

type redisSettings struct {
    Port int    `env:"REDIS_PORT"`
    Host string `env:"REDIS_HOST" required:"true"`
}

func main() {
    // Initialize with defaults (if zero value is not desired)
    settings := appSettings{
        Port: 80,
        Redis: redisSettings{
            Port: 6379,
        },
    }

    // Pull in environment variables
    err := envconfig.Unmarshal(&settings)
    if err != nil {
        fmt.Println(err)
        panic("failed to load configuration from environment, see above error")
    }

    // Print them out
    fmt.Println("Port:", settings.Port)
    fmt.Println("DB Connection:", settings.DBConnection)
    fmt.Println("Redis Port:", settings.Redis.Port)
    fmt.Println("Redis Host:", settings.Redis.Host)
}

This example will print out:

Port: 80
DB Connection: ...
Redis Port: 6379
Redis Host: ...

Functions

Below is documentation for exported functions:

func Unmarshal(i interface{}) error

Unmarshal dumps environment variable values into exported fields of a struct (pass a *struct) It will automatically look up environment variables that are named in a struct tag. For example, if you tag a field in your struct with env:"MY_VAR" it will be filled with the value of that environment variable. If you would like an error to be returned if the field is not set, use the tag required:"true". For boolean, fields, any of the following values are valid (any case): "true"/"false", "yes"/"no", "on"/"off", "t"/"f", "y"/"n", "1"/"0". Empty/unset environment variable values will not overwrite the struct fields that are already set. Any pointer fields will be dereferenced once (but are skipped if nil). Fields of a struct kind are unmarshalled recursively. Slices are supported with ":" separated strings (only string slices are supported though)

Supported Field Types

Currently, Unmarshal supports the following field types:

  • bool
  • float32 and float64
  • int, int8, int16, int32, and int64
  • []string
  • string
  • struct
  • uint, uint8, uint16, uint32, and uint64

Note: user-defined types that are defined using one of the above built-in types are also supported. For example:

type myCustomInt int

The above is perfectly fine and will work as well.

Contributing

Feel free to contribute by forking and creating a pull request. If you find any issues please post them here and I'll resolve them when I get a chance.

License

MIT License

Copyright © 2019 Caleb Everett

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.