在revel app.conf中读取环境变量

Question

Revel uses app.conf for storing configuration. I want my configuration to get value from environment variable using os.Getenv(key)

How can I do it? Should I use revel.Config to make changes? if so where do I place it?

Or is there another way?

I use it mainly for storing database information (I don't want to enter my credential in configuration files)

Thank you

Answer 1

Revel uses revel/config for managing app.conf.

And the only place revel/config foes read from the environment variable is in type.go (c *Config) String() method.

// $ environment variables
computedVal, _ = c.computeVar(&value, envVarRegExp, 2, 1, func(varName *string) string {
return os.Getenv(*varName)
})

That means you could add in a config file values based on the name of environment variable, which would allow you to use said environment variable to modify the config.

See an example in the revel/config REAMD.md file.

[DEFAULT]
host: www.example.com
protocol: http://
base-url: %(protocol)s%(host)s    <====

---

The OP pveyes points out to this comment in type.go:

// substitute by new value and take off leading '%(' and trailing ')s'
// %(foo)s => headsz=2, tailsz=2
// ${foo} => headsz=2, tailsz=1

So:

• when using environment variables use ${ENV_VARS}, and
• for unfolding variables use %(UNF_VARS)s