start commit, first version of golang application sample with configuration management and docker

config/Config.go

@@ -0,0 +1,30 @@
+package config
+
+import (
+	"github.com/ilyakaznacheev/cleanenv"
+	"sync"
+)
+
+type Config struct {
+	API struct {
+		Token string `env:"TOKEN" env-layout:"string" env-required:"true"`
+		Owner int `env:"OWNER" env-layout:"int" env-required:"true"`
+	}
+	Paths struct {
+		Docs string `env:"DOCS_PATH" env-layout:"string" env-default:"docs" env-upd:"true"`
+	}
+}
+
+var cfg Config
+var once sync.Once
+
+// panic
+func GetConfig() Config {
+	once.Do(func() {
+		err := cleanenv.ReadEnv(&cfg)
+		if err != nil {
+			panic(err.Error())
+		}
+	})
+	return cfg
+}

config/Config_test.go

@@ -0,0 +1,106 @@
+package config
+
+import (
+	"github.com/stretchr/testify/assert"
+	"os"
+	"strconv"
+	"sync"
+	"testing"
+)
+
+func TestGetConfig(t *testing.T) {
+	telegramToken := ":: telegram telegram token ::"
+	telegramOwner := 1234567890
+	pathDictionaries := `docs/dictionaries`
+
+	initTelegramBotEnvironment(telegramToken, telegramOwner, pathDictionaries)
+	defer cleanTelegramBotEnvironment()
+
+	var config Config
+	assert.NotPanics(t, func() { config = GetConfig() })
+
+	assert.NotEmpty(t, config)
+	assert.IsType(t, Config{}, config)
+	assert.Equal(t, telegramToken, config.API.Token)
+	assert.Equal(t, telegramOwner, config.API.Owner)
+	assert.Equal(t, pathDictionaries, config.Paths.Docs)
+}
+
+func TestGetConfigTwice(t *testing.T) {
+	initTelegramBotEnvironment(":: telegram telegram token ::", 1234567890, `docs/dictionaries`)
+	defer cleanTelegramBotEnvironment()
+
+	config1 := GetConfig()
+	config2 := GetConfig()
+
+	assert.NotEmpty(t, config1)
+	assert.NotEmpty(t, config2)
+	assert.Equal(t, config1, config2)
+	assert.NotSame(t, config1, config2)
+}
+
+func TestGetConfigAndSingletonIsImmutable(t *testing.T) {
+	telegramToken := ":: telegram telegram token ::"
+	telegramOwner := 1234567890
+	pathDictionaries := `docs/dictionaries`
+
+	initTelegramBotEnvironment(telegramToken, telegramOwner, pathDictionaries)
+	defer cleanTelegramBotEnvironment()
+
+	config1 := GetConfig()
+
+	assert.Equal(t, telegramToken, config1.API.Token)
+	assert.Equal(t, telegramOwner, config1.API.Owner)
+	assert.Equal(t, pathDictionaries, config1.Paths.Docs)
+
+	config1.API.Token = ":: some another telegram token ::"
+	config1.API.Owner = 1
+	config1.Paths.Docs = ":: some else path ::"
+	config2 := GetConfig()
+
+	assert.Equal(t, telegramToken, config2.API.Token)
+	assert.Equal(t, telegramOwner, config2.API.Owner)
+	assert.Equal(t, pathDictionaries, config2.Paths.Docs)
+}
+
+func TestGetConfigWithOnlyRequiredEnvironment(t *testing.T) {
+	telegramToken := ":: telegram telegram token ::"
+	telegramOwner := 1234567890
+
+	_ = os.Setenv("TOKEN", telegramToken)
+	_ = os.Setenv("OWNER", strconv.Itoa(telegramOwner))
+	defer cleanTelegramBotEnvironment()
+
+	config := GetConfig()
+
+	assert.NotEmpty(t, config)
+	assert.IsType(t, Config{}, config)
+	assert.Equal(t, telegramToken, config.API.Token)
+	assert.Equal(t, telegramOwner, config.API.Owner)
+	assert.Equal(t, `docs`, config.Paths.Docs)
+}
+
+func TestGetConfigWithEmptyEnvironment(t *testing.T) {
+	cleanTelegramBotEnvironment()
+
+	assert.Panics(t, func() { GetConfig() })
+}
+
+func initTelegramBotEnvironment(telegramToken string, telegramOwner int, pathDictionaries string) {
+	resetConfig()
+	_ = os.Setenv("TOKEN", telegramToken)
+	_ = os.Setenv("OWNER", strconv.Itoa(telegramOwner))
+	_ = os.Setenv("DOCS_PATH", pathDictionaries)
+}
+
+func cleanTelegramBotEnvironment() {
+	_ = os.Unsetenv("TOKEN")
+	_ = os.Unsetenv("OWNER")
+	_ = os.Unsetenv("DOCS_PATH")
+	resetConfig()
+}
+
+func resetConfig()  {
+	cfg = Config{}
+	once = sync.Once{}
+}