How to set environment variables that last

I'm trying to set some environment variables on my machine using Go OS

	err := os.Setenv("DBHOST", dbHostLocal)
	if err != nil {
		log.Fatalf("err %v", err)
	}

It seems the variable is available to the Go program but once I quite / terminate the Go process the variable is no longer available. I'm wondering if it's possible to set these variables permanently. The reason is that i was looking to create a "setup" file with config files ( db name etc ) for the local and dev environment so that I could switch between without any setup at all... just one time go run setup.go.

Short: It is not possible. You can't change the environment of your parent process. You can only change your own and pass it to your children.

What you should do is maintain a config file.
There are plenty of go config libs out there: ini, yaml, etc.

If your program changes the config, save it to disk after each change or one in a while or when the process exits.

Whilst not considered possible, if you're building some cli tool that exits you could consider outputting the equivalent shell to STDOUT like: docker-machine eval.

Quick and dirty example:

package main

import (
  "fmt"
  "reflect"
  "strings"
)

type config struct {
  db_host string
  db_port int
  db_user string
}

func main() {
  c := config{"db.example.com", 3306, "user1"}

  ct := reflect.ValueOf(&c).Elem()
  typeOfC := ct.Type()

  for i := 0; i < ct.NumField(); i++ {
    f := ct.Field(i)
    fmt.Printf("%s=%v\n", strings.ToUpper(typeOfC.Field(i).Name), f)
  }
}

Output:
$ go run env.go
DB_HOST=db.example.com
DB_PORT=3306
DB_USER=user1

You can then eval it on the command line and have access to those variables.

$ eval $(go run env.go)
$ echo $DB_HOST
db.example.com

The only way to get the behavior you want is to alter the environment of the current shell, and the easiest way is with a simple shell script

# setup.sh
export DBHOST="dbhost.url"
export CONFIG_VAR_TWO="testing"

and then

$ source setup.sh

It's possible if you write a value to the registry, but for this, your application needs administrator rights

func setEnvironment(key string, value string){
   k, err := registry.OpenKey(registry.LOCAL_MACHINE, `SYSTEM\ControlSet001\Control\Session Manager\Environment`, registry.ALL_ACCESS)
   if err != nil {
	   log.Fatal(err)
   }
   defer k.Close()

   err = k.SetStringValue(key, value)
   if err != nil {
	   log.Fatal(err)
   }
}