Environment variable is not set on terminal session after setting it with "os" package

Question

I have this code where I just want to set a environment variable:

package main

import (
    "os"
    "fmt"
)

func main() {
    _ = os.Setenv("FOO", "BAR")
    fmt.Println(os.Getenv("FOO"))
}

Running this file:

>$ go run file.go
BAR

The fmt.Println call prints BAR correctly, but then I expected this env variable to be set on my session as well, however:

>$ echo $FOO

>$

There's nothing on $FOO, it is empty. Is this a expected behavior? If so, how can I make this env variable to persist on my session setting it with a go program like this?

Answer 1

Not sure this is ultimately what you want to do, but it does give you the result you asked for.

package main
import (
        "os"
        "syscall"
)
func main() {
        os.Setenv("FOO", "BAR")
        syscall.Exec(os.Getenv("SHELL"), []string{os.Getenv("SHELL")}, syscall.Environ())
}

This replaces the go process with a new shell with the modified environment.

You probably would want to call it as "exec APPNAME", as that will avoid having a shell in a shell.

example:

#!/bin/bash
exec go-env-setter-app

you will end up with a bash shell with the modified environment