Support .env files

[goliatone]

Explore supporting dotenv configuration files.

[goliatone]

Support:

• .env
• .secrets.env
  This would be regular files with content such as:

HOST=xxx.xxx.xxx.xxx
USERNAME=<username>
PASSWORD=<upassword>
HONEYBADGER_KEY=<honeybadger key>
QUEUE_ENDPOINT=<ampq://>

Another case would be when we have multiple files with different values for the same set of env vars:

• secrets.west.env, secrets.east.env

secrets.west.env

HOST=192.18.1.13

secrets.east.env

HOST=192.18.32.23