DotEnv in Golang

.env.example

KEY_A=value-a
KEY_B=value-b
KEY_C=value-c
DB_HOST=postgres.database.com
DB_PASSWORD=dr.i,G<I=!B3f[U8Qg%z9oP}FqYn\r

config.go

package config

import (
	"bufio"
	"log"
	"os"
	"regexp"
)

func LoadFile(filepath string) (*os.File, error) {
	file, err := os.Open(filepath)
	if err != nil {
		return nil, err
	}

	return file, nil
}

func ParseFile(file *os.File) map[string]string {
	result := make(map[string]string)
	scanner := bufio.NewScanner(file)
	regex, _ := regexp.Compile(`(\w+)=(.+)`)

	for scanner.Scan() {
		line := scanner.Text()

		matches := regex.FindAllStringSubmatch(line, -1)
		for _, match := range matches {
			log.Println("[config.ParseFile] ", match[1], match[2])
			result[match[1]] = match[2]
		}
	}

	return result
}

func SetEnvVariables(envVariables map[string]string) {
	for k, v := range envVariables {
		log.Println("[config.SetEnvVariables]", k, v)
		os.Setenv(k, v)
	}
}

config_test.go

package config

import (
	"os"
	"testing"
)

var envFile = ".env.example"

func TestLoadFile(t *testing.T) {
	result, _ := LoadFile(envFile)
	if result == nil {
		t.Error("file should not be nil")
	}
}

func TestParseFile(t *testing.T) {
	file, _ := LoadFile(envFile)
	lines := ParseFile(file)
	if lines == nil {
		t.Error("should return file lines")
	}

	if value, ok := lines["KEY_A"]; !ok {
		t.Error("should have the key", value)
	}

	if value := lines["KEY_A"]; value != "value-a" {
		t.Error("should have right value", value)
	}

	if value, ok := lines["DB_HOST"]; !ok {
		t.Error("should have the key DB_HOST", value)
	}

	if value := lines["DB_HOST"]; value != "postgres.database.com" {
		t.Error("should have right value", value)
	}
}

func TestEnvVariables(t *testing.T) {
	file, _ := LoadFile(envFile)
	envVars := ParseFile(file)
	SetEnvVariables(envVars)

	for k, v := range envVars {
		if value := os.Getenv(k); value != v {
			t.Error("should setup the right value", k, v)
		}
	}
}