Environment variables

Context

Environment variables are key‑value pairs that configure the operating system environment. In Go, use os.Getenv to read them, os.Setenv to set them, and os.Unsetenv to delete them.

Example

Read the HOME variable and a custom APP_MODE variable.

Code example

package main

import (
    "fmt"
    "os"
)

func main() {
    home := os.Getenv("HOME")
    fmt.Println("Home:", home)

    mode := os.Getenv("APP_MODE")
    if mode == "" {
        mode = "development"
    }
    fmt.Println("Mode:", mode)

    // Lookup with ok
    if val, ok := os.LookupEnv("PATH"); ok {
        fmt.Println("PATH exists")
    }
}

Output

Home: /home/user
Mode: development
PATH exists

Useful links

• os package: Environment variables
• 12 Factor App: Config