This example demonstrates how to declare an environment variable that produces a
time.Durationvalue, but Ferrite supports many different variable types, as described in the examples.
First, describe the application's environment variables using Ferrite's
"builder" interfaces. This is typically done at the package-scope of the main
package.
var httpTimeout = ferrite.
Duration("HTTP_TIMEOUT", "the maximum duration of each HTTP request").
WithDefault(10 * time.Second).
Required()Next, initialize Ferrite in the application's main() function before any other
code is executed so that it may halt execution when the environment is invalid.
func main() {
ferrite.Init()
// existing application logic ...
}Finally, read the environment variable's value by calling the Value() method.
timeout := httpTimeout.Value()
ctx, cancel := context.WithTimeout(context.Background(), timeout)
defer cancel()
// do HTTP request ...By default, calling Init() operates in "validation" mode. There are several
other modes that can be used to gain insight into the application's use of
environment variables.
Modes are selected by setting the FERRITE_MODE environment variable.
This is the default mode. If one or more environment variables are invalid, this
mode renders a description of all declared environment variables and their
associated values and validation failures to STDERR, then exits the process
with a non-zero exit code.
It also shows warnings if deprecated environment variables are used.
This mode renders Markdown documentation about the environment variables to
STDOUT. The output is designed to be included in the application's README.md
file or a similar file.
This mode renders environment variables to STDOUT in a format suitable for use
with tools like dotenv and the
env_file directive
in Docker compose files.
Austenite is a TypeScript library with similar features to Ferrite.