micro/config/source/env/README.md
2019-05-30 23:11:13 +01:00

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# Env Source
The env source reads config from environment variables
## Format
We expect environment variables to be in the standard format of FOO=bar
Keys are converted to lowercase and split on underscore.
### Example
```
DATABASE_ADDRESS=127.0.0.1
DATABASE_PORT=3306
```
Becomes
```json
{
"database": {
"address": "127.0.0.1",
"port": 3306
}
}
```
## Prefixes
Environment variables can be namespaced so we only have access to a subset. Two options are available:
```
WithPrefix(p ...string)
WithStrippedPrefix(p ...string)
```
The former will preserve the prefix and make it a top level key in the config. The latter eliminates the prefix, reducing the nesting by one.
#### Example:
Given ENVs of:
```
APP_DATABASE_ADDRESS=127.0.0.1
APP_DATABASE_PORT=3306
VAULT_ADDR=vault:1337
```
and a source initialized as follows:
```
src := env.NewSource(
env.WithPrefix("VAULT"),
env.WithStrippedPrefix("APP"),
)
```
The resulting config will be:
```
{
"database": {
"address": "127.0.0.1",
"port": 3306
},
"vault": {
"addr": "vault:1337"
}
}
```
## New Source
Specify source with data
```go
src := env.NewSource(
// optionally specify prefix
env.WithPrefix("MICRO"),
)
```
## Load Source
Load the source into config
```go
// Create new config
conf := config.NewConfig()
// Load file source
conf.Load(src)
```