add postgres and refactor code

main.go

@@ -7,7 +7,7 @@ import (
 	"astra-users/mw"
 	"github.com/labstack/echo/v4"
 	"github.com/labstack/echo/v4/middleware"
-	"gorm.io/driver/sqlite"
+	"gorm.io/driver/postgres"
 	"gorm.io/gorm"
 	"gorm.io/gorm/logger"
 	"log"
@@ -27,7 +27,7 @@ func main() {
 		},
 	)
 
-	db, err := gorm.Open(sqlite.Open(config.Env.Server.ConnectionString), &gorm.Config{
+	db, err := gorm.Open(postgres.Open(config.Env.Server.ConnectionString), &gorm.Config{
 		Logger: newLogger,
 	})
 	if err != nil {