A no-nonsense guide to environment variables in Go- 2 mins
Environment variables are the best way to set configuration values for your software application as they can be defined at system-level, independently of the software. This is one of the principles of the Twelve-Factor App methodology and enables applications to be built with portability.
Using environment variables
All you need to interact with environment variables is the standard
os package. Here is an example of how you can access the system
PATH environment variable.
It’s equally easy to set environment variables:
Loading environment variables from a .env file
It is not always practical to set environment variables on development machines where multiple projects are running.
To install the package run:
$ go get github.com/joho/godotenv
Add your configuration values to a
.env file at the root of your project:
Then you can use these values in your application:
It’s important to note that if an environment variable is already defined in the system, then Go will prefer use that instead of the value in
Wrapping environment variables in a configuration package
It’s all well and good accessing environment variables directly like this, but having to maintain that doesn’t seem fun, does it? Every value is a string - and imagine having to update every reference when an environment key is modified!
To deal with this, let’s create a configuration package to access environment variables in a much more centralized and maintainable way.
Here is a simple
config package which will return configuration values in a
Config struct. We have the option to define a default value, so when an environment variable does not exist this will be used instead.
Next, we should add different types to the
Config struct. The current implementation can only handle
string types, which isn’t very practical for larger applications.
Let’s add functions to handle
.env file with these environment variables.
GITHUB_USERNAME=craicoverflow GITHUB_API_KEY=TCtQrZizM1xeo1v92lsVfLOHDsF7TfT5lMvwSno MAX_USERS=10 USER_ROLES=admin,super_admin,guest DEBUG_MODE=false
And now you can access these values from the rest of your application:
And there you have it
There are several libraries out there that claim to offer a configuration “solution” for your Go application. But is it really a solution when it’s just as easy to make one yourself?
How do you manage configuration in your Go applications?