Hai everyone, long time no see… I would like to share important information according to the title above.

We know that using env on golang project is very important and useful because with env we can manage the configuration in different development environments like development, staging and production. Without env we will have trouble changing the development environment from development to staging and vice versa.

In the golang project there are 2 libraries that are often used, godotenv and viper.

go get

go get github.com/spf13/viper

Ok let's create the new project:

mkdir golang-viper
cd golang-viper
code .

Add go.mod with the same name project or other:

go mod init golang-viper

Install the godotenv and viper packages:

go get github.com/spf13/viper
go get github.com/joho/godotenv

Using Viper 

Create a new file main.go and copy the following code:

package main

import (
 "fmt"
 "os"

 "github.com/spf13/viper"
)

func main() {
 viper.AddConfigPath("env")
 viper.SetConfigType("env")
 viper.SetConfigName("app")
 err := viper.ReadInConfig() // Find and read the config file
 if err != nil {             // Handle errors reading the config file
  panic(fmt.Errorf("fatal error config file: %w", err))
 }

 fmt.Println("DB_HOST from config:", viper.GetString("DB_HOST"))
 fmt.Println("DB_PORT from config:", viper.GetString("DB_PORT"))
}

Explained:

• viper.AddConfigPath("env") location env on your project, this project env in env directory.
• viper.SetConfigType("env") type of env file, in viper we use env, yaml and json file. This project uses env file.
• viper.SetConfigName("app") Name of the env file. This project env file will have the name app.env. You can create env file like app.env or app.yaml or app.json.

Next to read the configuration from env file you need to add viper.ReadConfig(). Next, to read the contents of the env we use viper.getString and put the key env file.

Below is the contents of the env file:

DB_HOST=localhost
DB_PORT=5432

Run the project:

go run .

➜  golang-viper go run . 
DB_HOST from config: localhost
DB_PORT from config: 5432
➜  golang-viper 

Using Godotenv 

Using this library is very simple and easy, just put the code below on your configuration file:

package main

import (
    "log"
    "os"

    "github.com/joho/godotenv"
)

func main() {
  err := godotenv.Load()
  if err != nil {
    log.Fatal("Error loading .env file")
  }

  dbHost := os.Getenv("DB_HOST")
  dbPort := os.Getenv("DB_PORT")

  fmt.Println("dbHost: ", dbHost)
  fmt.Println("dbPort: ", dbPort)
}

Yes very easy with godotenv just put:

godotenv.Load()

Run the project:

➜  golang-viper go run . 
dbHost: localhost
dbPort: 5432
➜  golang-viper

Conclusion

• Using godotenv and viper actually depends on the project being made, if it's a simple project using godotenv is the right choice.
• The use of different env file options and we can flexibly set the viper option is the right one.

See you on next article...