How to Assign Default Values for Nil Environment Variables in Go?

Assigning Default Values for Nil Environment Variables in Go

In Go, unlike Python's os.getenv() function, there is no built-in mechanism to assign a default value if an environment variable is not set. To address this issue, the following approaches can be employed:

Option 1: Using an if-else Block

Although relying on if-else statements to check variable states is generally discouraged, it can be used to assign default values for environment variables:

var mongoPassword string
if mongoPass := os.Getenv("MONGO_PASS"); mongoPass != "" {
    mongoPassword = mongoPass
} else {
    mongoPassword = "pass"
}

Option 2: Creating a Helper Function

For multiple environment variables, creating a helper function provides a cleaner approach:

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

To use it:

mongoPassword := getenv("MONGO_PASS", "pass")

Option 3: Using os.LookupEnv(key) Boolean

os.LookupEnv returns two values: the value and its existence status. This can be used to set a default value as follows:

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

Note that if the environment variable's value is empty, the fallback value will be assigned instead.

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