initial commit, adding SQL connection and a simple testing on main

app/libs/database/db.go

@@ -0,0 +1,42 @@
+package database
+
+import (
+	"log"
+
+	"github.com/joho/godotenv"
+	"github.com/spf13/viper"
+	"gorm.io/driver/mysql"
+	"gorm.io/gorm"
+)
+
+var shared_db_connection *gorm.DB
+
+func initDB() *gorm.DB {
+	// load .env into environment (so viper can read them)
+	if err := godotenv.Load(); err != nil {
+		log.Println(".env not found or could not be loaded; proceeding with existing environment variables")
+	}
+
+	viper.AutomaticEnv() // read from environment
+
+	sql_dsn := viper.GetString("SQL_DSN")
+
+	if sql_dsn == "" {
+		log.Fatal("SQL_DSN must be set in .env or environment")
+	}
+
+	db, err := gorm.Open(mysql.Open(sql_dsn), &gorm.Config{})
+	if err != nil {
+		log.Fatalf("failed to connect to MySQL Server: %v", err)
+	}
+
+	log.Println("connected to MySQL Server")
+	return db
+}
+
+func Init() *gorm.DB {
+	if shared_db_connection == nil {
+		shared_db_connection = initDB()
+	}
+	return shared_db_connection
+}