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132 lines
4 KiB
Markdown
132 lines
4 KiB
Markdown
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# gotenv
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[](https://travis-ci.org/subosito/gotenv)
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[](https://ci.appveyor.com/project/subosito/gotenv/branch/master)
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[](https://codecov.io/gh/subosito/gotenv)
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[](https://goreportcard.com/report/github.com/subosito/gotenv)
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[](https://godoc.org/github.com/subosito/gotenv)
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Load environment variables dynamically in Go.
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## Usage
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Put the gotenv package on your `import` statement:
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```go
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import "github.com/subosito/gotenv"
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```
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To modify your app environment variables, `gotenv` expose 2 main functions:
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- `gotenv.Load`
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- `gotenv.Apply`
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By default, `gotenv.Load` will look for a file called `.env` in the current working directory.
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Behind the scene, it will then load `.env` file and export the valid variables to the environment variables. Make sure you call the method as soon as possible to ensure it loads all variables, say, put it on `init()` function.
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Once loaded you can use `os.Getenv()` to get the value of the variable.
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Let's say you have `.env` file:
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```
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APP_ID=1234567
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APP_SECRET=abcdef
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```
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Here's the example of your app:
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```go
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package main
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import (
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"github.com/subosito/gotenv"
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"log"
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"os"
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)
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func init() {
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gotenv.Load()
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}
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func main() {
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log.Println(os.Getenv("APP_ID")) // "1234567"
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log.Println(os.Getenv("APP_SECRET")) // "abcdef"
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}
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```
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You can also load other than `.env` file if you wish. Just supply filenames when calling `Load()`. It will load them in order and the first value set for a variable will win.:
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```go
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gotenv.Load(".env.production", "credentials")
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```
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While `gotenv.Load` loads entries from `.env` file, `gotenv.Apply` allows you to use any `io.Reader`:
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```go
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gotenv.Apply(strings.NewReader("APP_ID=1234567"))
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log.Println(os.Getenv("APP_ID"))
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// Output: "1234567"
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```
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Both `gotenv.Load` and `gotenv.Apply` **DO NOT** overrides existing environment variables. If you want to override existing ones, you can see section below.
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### Environment Overrides
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Besides above functions, `gotenv` also provides another functions that overrides existing:
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- `gotenv.OverLoad`
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- `gotenv.OverApply`
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Here's the example of this overrides behavior:
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```go
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os.Setenv("HELLO", "world")
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// NOTE: using Apply existing value will be reserved
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gotenv.Apply(strings.NewReader("HELLO=universe"))
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fmt.Println(os.Getenv("HELLO"))
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// Output: "world"
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// NOTE: using OverApply existing value will be overridden
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gotenv.OverApply(strings.NewReader("HELLO=universe"))
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fmt.Println(os.Getenv("HELLO"))
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// Output: "universe"
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```
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### Throw a Panic
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Both `gotenv.Load` and `gotenv.OverLoad` returns an error on something wrong occurred, like your env file is not exist, and so on. To make it easier to use, `gotenv` also provides `gotenv.Must` helper, to let it panic when an error returned.
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```go
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err := gotenv.Load(".env-is-not-exist")
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fmt.Println("error", err)
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// error: open .env-is-not-exist: no such file or directory
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gotenv.Must(gotenv.Load, ".env-is-not-exist")
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// it will throw a panic
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// panic: open .env-is-not-exist: no such file or directory
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```
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### Another Scenario
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Just in case you want to parse environment variables from any `io.Reader`, gotenv keeps its `Parse` and `StrictParse` function as public API so you can use that.
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```go
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// import "strings"
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pairs := gotenv.Parse(strings.NewReader("FOO=test\nBAR=$FOO"))
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// gotenv.Env{"FOO": "test", "BAR": "test"}
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err, pairs = gotenv.StrictParse(strings.NewReader(`FOO="bar"`))
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// gotenv.Env{"FOO": "bar"}
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```
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`Parse` ignores invalid lines and returns `Env` of valid environment variables, while `StrictParse` returns an error for invalid lines.
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## Notes
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The gotenv package is a Go port of [`dotenv`](https://github.com/bkeepers/dotenv) project with some additions made for Go. For general features, it aims to be compatible as close as possible.
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