Reading and setting environment variables

Environment variables are another way to pass state into an application beyond reading data in from a file or passing it explicitly over the command line. This recipe will explore some very basic getting and setting of environment variables and then work with the highly useful third-party library https://github.com/kelseyhightower/envconfig.

We'll build an application that can read a config via JSON or through environment variables. The next recipe will further explore alternative formats, including TOML and YAML.

Getting ready

Configure your environment according to these steps:

1. Refer to the Getting ready section's steps in the Using command-line flags recipe.
2. Run the go get github.com/kelseyhightower/envconfig/ command.
3. Run the go get github.com/pkg/errors/ command.

How to do it...

These steps cover writing and running your application:

1. From your terminal/console application, create a new directory called chapter2/envvar and navigate to that directory.

2. Copy...