enable using a function "file" to read file content directly on .env file

[jjangga0214]

It has been inconvenient specifying very long value which originally should be contained in a file (e.g. private/public keys). There also have been requests for easier multiline use (e.g. #196).

Therefore I suggest a built-in function, file.

FOO=foo
BAR=bar
PRIVATE_KEY=file(path/to/file)

This would read file content from the given path (argument).

No more manually making a multiline value to single line, and replacing \\n to \n.

Maybe we can generalize the idea to enable other functions if desired. For example, special characters indicating a function like #function# or $function$.

[maxbeatty]

Yes, I agree it makes more sense to store (very) long values in separate files instead of manually altering them to a single line in .env files. Instead of creating new syntax to be interpreted by dotenv, you could just use Node.js.

PRIVATE_KEY_PATH=path/to/file

require("dotenv").config()

process.env.PRIVATE_KEY = require("fs").readFileSync(process.env.PRIVATE_KEY_PATH)