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kelseyhightower / envconfig

Golang library for managing configuration data from environment variables
MIT License
5.02k stars 377 forks source link

Reference to other environment variables in `default` #83

Closed tchap closed 7 years ago

tchap commented 7 years ago

Hi,

I am embedding one config struct in another. The embedded struct is used across multiple projects. What I would need is to be able to set different default values based on the project, which is not possible since the tag value is static.

An example could be that I would like to use the value of SERVICE_NAME environment variable in the embedded config struct as the default value for something.

I am probably going to fork this package and implement it so that when there is default:"$SERVICE_NAME", the relevant environment variable is used as the default value. I am just wondering whether to send a PR afterwards. Does it seem handy for other people?

Or perhaps you want to implement it yourself quickly. It's just about checking whether default starts with $ or any other magical prefix and act accordingly...

Cheers!

teepark commented 7 years ago

I'd recommend against that approach -- it's starting to turn struct field tags into a mini DSL. A tiny bit of code wrapping the envconfig.Process could handle this for you. Logic like "try this env var, then fallback here" is getting a little involved for envconfig to tackle directly.

tchap commented 7 years ago

Right. I will think about your advice. Thanks!