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https://github.com/vrischmann/envconfig

Small library to read your configuration from environment variables
https://github.com/vrischmann/envconfig

configuration go golang

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Small library to read your configuration from environment variables

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envconfig

=========



![CI](https://github.com/vrischmann/envconfig/workflows/CI/badge.svg)

[![Go Reference](https://pkg.go.dev/badge/github.com/vrischmann/envconfig.svg)](https://pkg.go.dev/github.com/vrischmann/envconfig)



envconfig is a library which allows you to parse your configuration from environment variables and fill an arbitrary struct.



See [the example](https://godoc.org/github.com/vrischmann/envconfig#example-Init) to understand how to use it, it's pretty simple.



Supported types

---------------



  * Almost all standard types plus `time.Duration` are supported by default.

  * Slices and arrays

  * Arbitrary structs

  * Custom types via the [Unmarshaler](https://godoc.org/github.com/vrischmann/envconfig/#Unmarshaler) interface.



How does it work

----------------



*envconfig* takes the hierarchy of your configuration struct and the names of the fields to create a environment variable key.



For example:



```go

var conf struct {

    Name string

    Shard struct {

        Host string

        Port int

    }

}

```



This will check for those 3 keys:



  * NAME or name

  * SHARD\_HOST, or shard\_host

  * SHARD\_PORT, or shard\_port



Flexible key naming

-------------------



*envconfig* supports having underscores in the key names where there is a _word boundary_. Now, that term is not super explicit, so let me show you an example:



```go

var conf struct {

    Cassandra struct {

        SSLCert string

        SslKey string

    }

}

```



This will check all of the following keys:



  * CASSANDRA\_SSL\_CERT, CASSANDRA\_SSLCERT, cassandra\_ssl\_cert, cassandra\_sslcert

  * CASSANDRA\_SSL\_KEY, CASSANDRA\_SSLKEY, cassandra\_ssl\_key, cassandra\_sslkey



If that is not good enough, look just below.



Custom environment variable names

---------------------------------



*envconfig* supports custom environment variable names:



```go

var conf struct {

    Name string `envconfig:"myName"`

}

```



Default values

--------------



*envconfig* supports default values:



```go

var conf struct {

    Name string `envconfig:"default=Vincent"`

}

```



Optional values

---------------



*envconfig* supports optional values:



```go

var conf struct {

    Name string `envconfig:"optional"`

}

```



Skipping fields

---------------



*envconfig* supports skipping struct fields:

```go

var conf struct {

    Internal string `envconfig:"-"`

}

```



Combining multiple options in one tag

-------------------------------------



You can of course combine multiple options:



```go

var conf struct {

    Name string `envconfig:"default=Vincent,myName"`

}

```



Slices or arrays

----------------



With slices or arrays, the same naming is applied for the slice. To put multiple elements into the slice or array, you need to separate

them with a *,* (will probably be configurable in the future, or at least have a way to escape)



For example:



```go

var conf struct {

    Ports []int

}

```



This will check for the key __PORTS__:



  * if your variable is *9000* the slice will contain only 9000

  * if your variable is *9000,100* the slice will contain 9000 and 100



For slices of structs, it's a little more complicated. The same splitting of slice elements is done with a *comma*, however, each token must follow

a specific format like this: `{,,...}`



For example:



```go

var conf struct {

    Shards []struct {

        Name string

        Port int

    }

}

```



This will check for the key __SHARDS__. Example variable content: `{foobar,9000},{barbaz,20000}`



This will result in two struct defined in the *Shards* slice.



If you want to set default value for slice or array, you have to use `;` as separator, instead of `,`:



```go

var conf struct {

    Ports []int `envconfig:"default=9000;100"`

}

```



Same for slices of structs:



```go

var conf struct {

    Shards []struct {

        Name string

        Port int

    } `envconfig:"default={foobar;localhost:2929};{barbaz;localhost:2828}"`

}

```



Development state

-----------------



I consider _envconfig_ to be pretty much done.



It has been used extensively at [Batch](https://batch.com) for more than 5 years now without much problems,

with no need for new features either.



So, while I will keep maintaining this library (fixing bugs, making it compatible with new versions of Go and so on) for

the foreseeable future, I don't plan on adding new features.



But I'm open to discussion so if you have a need for a particular feature we can discuss it.