How to assign default value if env var is empty?

environment-variables, go

Solution

There's no built-in to fall back to a default value, so you have to do a good old-fashioned if-else.

But you can always create a helper function to make that easier:

func getenv(key, fallback string) string {
    value := os.Getenv(key)
    if len(value) == 0 {
        return fallback
    }
    return value
}

Note that as @michael-hausenblas pointed out in a comment, keep in mind that if the value of the environment variable is really empty, you will get the fallback value instead.

Even better as @ŁukaszWojciechowski pointed out, using `os.LookupEnv`:

func getEnv(key, fallback string) string {
    if value, ok := os.LookupEnv(key); ok {
        return value
    }
    return fallback
}

Problem

How do you assign a default value if an environment variable isn't set in Go? In Python I could do `mongo_password = os.getenv('MONGO_PASS', 'pass')` where `pass` is the default value if `MONGO_PASS` env var isn't set. I tried an if statement based on `os.Getenv` being empty, but that doesn't seem to work due to the scope of variable assignment within an if statement. And I'm checking for multiple env var's, so I can't act on this information within the if statement.

Original source