iamolegga/enviper

# enviper

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Package enviper is a helper/wrapper for [viper](http://github.com/spf13/viper) with the same API.
It makes it possible to unmarshal config to struct considering environment variables.

## Problem

[Viper](https://github.com/spf13/viper) package doesn't consider environment variables while unmarshaling.
Please, see: [188](https://github.com/spf13/viper/issues/188) and [761](https://github.com/spf13/viper/issues/761)

## Solution

Just wrap viper instance and use the same `Unmarshal` method as you did before:

```go
e := enviper.New(viper.New())
e.Unmarshal(&config)
```

## Example

```go
package main

import (
    "github.com/iamolegga/enviper"
    "github.com/spf13/viper"
)

type barry struct {
    Bar int `mapstructure:"bar"`
}
type bazzy struct {
    Baz bool
}
type quxxy struct {
    Qux string
}
type config struct {
    Foo      string
    Barry    barry
    Barries  map[string]barry
    Bazzy    bazzy `mapstructure:",squash"`
    Quxxy    *quxxy
}

// For example this kind of structure can be unmarshaled with next yaml:
//  Foo: foo
//  Barry:
//    bar: 42
//  Baz: true
//  Barries: 
//    key1:
//      Bar: 255
//    key2:
//      Bar: 256
//  Quxxy:
//    Qux: "lorem"
//
// And then it could be overriden by next env variables:
//  FOO=foo
//  BARRY_BAR=42
//  BAZ=true
//  BARRIES_KEY1_BAR=42
//  QUXXY_QUX=ipsum
//
// Or with prefix:
//  MYAPP_FOO=foo
//  MYAPP_BARRY_BAR=42
//  MYAPP_BAZ=true
//  MYAPP_BARRIES_KEY1_BAR=42
//  MYAPP_QUXXY_QUX=ipsum

func main() {    
    var c config

    e := enviper.New(viper.New())
    e.SetEnvPrefix("MYAPP")
    e.AddConfigPath("/my/config/path")
    e.SetConfigName("config")

    e.Unmarshal(&c)
}
```

## Custom Tag Names

In case you want to use custom tag name (something different from `mapstructure`), you have to set it explicitly via `WithTagName` function.
The wrapper must know custom tag name in order to register all the env vars for viper so you can't just use `DecoderConfigOption`.

## Credits

Thanks to
[krak3n](https://github.com/krak3n) ([issuecomment-399884438](https://github.com/spf13/viper/issues/188#issuecomment-399884438))
and
[celian-garcia](https://github.com/celian-garcia) ([issuecomment-626122696](https://github.com/spf13/viper/issues/761#issuecomment-626122696))
for inspiring.