feat(orm): add postgres connection handler for gorm

orm/postgres.go

@@ -0,0 +1,48 @@
+package orm
+
+import (
+    "log"
+    "os"
+    "sync"
+
+    "github.com/adhocore/urlsh/model"
+    "gorm.io/driver/postgres"
+    "gorm.io/gorm"
+    "gorm.io/gorm/logger"
+)
+
+var conn *gorm.DB
+
+func pgConnect() *gorm.DB {
+    dsn := os.Getenv("APP_DB_DSN")
+    if dsn == "" {
+        log.Fatal("Database configuration DSN missing, Pass in APP_DB_DSN env")
+    }
+
+    logLevel := logger.Warn
+    if os.Getenv("APP_ENV") == "prod" {
+        logLevel = logger.Silent
+    }
+
+    db, err := gorm.Open(postgres.Open(dsn), &gorm.Config{
+        Logger: logger.Default.LogMode(logLevel),
+    })
+
+    if err != nil {
+        log.Fatal("Cannot connect to database with given DSN")
+    }
+
+    _ = db.AutoMigrate(&model.Keyword{}, &model.Url{})
+
+    return db
+}
+
+var once sync.Once
+
+func Connection() *gorm.DB {
+    once.Do(func() {
+        conn = pgConnect()
+    })
+
+    return conn
+}