feat(ws): config package to load env and flags

backend/services/ws/internal/config/config.go

@@ -0,0 +1,103 @@
+// Loads environemnt variables and returns a config struct
+package config
+
+import (
+	"flag"
+	"log"
+	"os"
+	"strconv"
+
+	"github.com/joho/godotenv"
+)
+
+type Config struct {
+	Port  string // server port: e.g. ":8080"
+	Token string // controller auth token
+}
+
+func NewConfig() Config {
+
+	//Defines log format
+	log.SetFlags(log.LstdFlags | log.Lshortfile)
+
+	loadEnv()
+
+	/*
+		App variables priority:
+		1º - Flag through command line.
+		2º - Env variables.
+		3º - Default flag value.
+	*/
+
+	/* ------------------------------ define flags ------------------------------ */
+	flPort := flag.String("port", lookupEnvOrString("SERVER_PORT", ":8080"), "Server port")
+	flToken := flag.String("token", lookupEnvOrString("SERVER_AUTH_TOKEN", ""), "Controller auth token")
+	flHelp := flag.Bool("help", false, "Help")
+	flag.Parse()
+	/* -------------------------------------------------------------------------- */
+
+	if *flHelp {
+		flag.Usage()
+		os.Exit(0)
+	}
+
+	return Config{
+		Port:  *flPort,
+		Token: *flToken,
+	}
+}
+
+// Load environment variables from .env or .env.local file
+func loadEnv() {
+	err := godotenv.Load()
+	if err != nil {
+		log.Println("Error to load environment variables:", err)
+	}
+
+	localEnv := ".env.local"
+	if _, err := os.Stat(localEnv); err == nil {
+		_ = godotenv.Overload(localEnv)
+		log.Println("Loaded variables from '.env.local'")
+	} else {
+		log.Println("Loaded variables from '.env'")
+	}
+}
+
+/* ---------------------------- helper functions ---------------------------- */
+/*
+	They are used to lookup if a environment variable is set with a value
+	different of "" and return it.
+	In case the var doesn't exist, it returns the default value.
+	Also, they're useful to convert the string value of vars to the desired type.
+*/
+
+func lookupEnvOrString(key string, defaultVal string) string {
+	if val, _ := os.LookupEnv(key); val != "" {
+		return val
+	}
+	return defaultVal
+}
+
+func lookupEnvOrInt(key string, defaultVal int) int {
+	if val, _ := os.LookupEnv(key); val != "" {
+		v, err := strconv.Atoi(val)
+		if err != nil {
+			log.Fatalf("LookupEnvOrInt[%s]: %v", key, err)
+		}
+		return v
+	}
+	return defaultVal
+}
+
+func lookupEnvOrBool(key string, defaultVal bool) bool {
+	if val, _ := os.LookupEnv(key); val != "" {
+		v, err := strconv.ParseBool(val)
+		if err != nil {
+			log.Fatalf("LookupEnvOrBool[%s]: %v", key, err)
+		}
+		return v
+	}
+	return defaultVal
+}
+
+/* -------------------------------------------------------------------------- */