Chapter 19: Configuration

19.1 The "Twelve-Factor" Philosophy

Why do we do this? Hardcoding values (like port = 8080) is the mark of a beginner. Professional apps follow the 12-Factor App methodology. Factor III: "Store config in the environment".

Comparison: Configuration

Language	Beginner Approach	Professional Approach
Python	PORT = 8000 top of file	os.environ.get('PORT')
Java	application.properties	System Properties / Env Vars
Go	const Port = ":8080"	os.Getenv("PORT")

19.2 Reading the Environment

func LoadConfig() Config {
    return Config{
        Port: os.Getenv("PORT"),
    }
}

Anatomy of os.Getenv

1. os: Standard library package for Operating System functions.
2. Getenv: "Get Environment Variable".
3. ("PORT"): The key we are looking for.
   • If the computer has PORT=9090 set in its memory, this function returns "9090".
   • If not, it returns "" (Empty String).

Professional apps often assume a default if the result is empty:

port := os.Getenv("PORT")
if port == "" {
    port = "8081" // Default fallback
}

🎓 Knowledge Check: Why do we read configuration from "Environment Variables"?

Answer: To follow the 12-Factor App methodology. This allows us to change settings (changing ports, database passwords) without changing the code itself or recompiling.