Overview

gotenv package in golang can be used to load .env or environment file in golang
https://github.com/joho/godotenv

Below is the signature of the function

func Load(filenames ...string) (err error) 

It takes a variable number of arguments where each argument can be the .env filenames that it needs to load

Program

Create a file local.env with below contents

STACK=DEV
DATABASE=SQL

Here is the program

package main

import (
	"fmt"
	"log"
	"os"

	"github.com/joho/godotenv"
)

func main() {
	err := godotenv.Load("local.env")
	if err != nil {
		log.Fatalf("Some error occured. Err: %s", err)
	}

	val := os.Getenv("STACK")
	fmt.Println(val)

	val = os.Getenv("DATABASE")
	fmt.Println(val)
}

Output

DEV
SQL

It loads the local.env file and gives the correct output

It can also be used to load multiple .env files. Create a new file test.env with below contents

TEST=UNIT

package main

import (
	"fmt"
	"log"
	"os"

	"github.com/joho/godotenv"
)

func main() {
	err := godotenv.Load("local.env", "test.env")
	if err != nil {
		log.Fatalf("Some error occured. Err: %s", err)
	}

	val := os.Getenv("STACK")
	fmt.Println(val)

	val = os.Getenv("DATABASE")
	fmt.Println(val)

	val = os.Getenv("TEST")
	fmt.Println(val)
}

Output

DEV
SQL
UNIT

If you don’t supply any argument to the Load function then by default it will load the file named .env in the current directory.

Create a file named .env with the below contents in the current directory

STACK=DEV
DATABASE=SQL

package main

import (
	"fmt"
	"log"
	"os"

	"github.com/joho/godotenv"
)

func main() {
	err := godotenv.Load()
	if err != nil {
		log.Fatalf("Some error occured. Err: %s", err)
	}

	val := os.Getenv("STACK")
	fmt.Println(val)

	val = os.Getenv("DATABASE")
	fmt.Println(val)
}

Notice in the above program that we didn’t pass any argument to the Load function

Output

DEV
SQL

This was about loading .env files in golang

Note: Check out our Golang Advanced Tutorial. The tutorials in this series are elaborative and we have tried to cover all concepts with examples. This tutorial is for those who are looking to gain expertise and a solid understanding of golang – Golang Advance Tutorial

Also if you are interested in understanding how all design patterns can be implemented in Golang. If yes, then this post is for you –All Design Patterns Golang