[Add] ConnectionLimit option

@@ -3,8 +3,6 @@
 [![puppeteer](https://img.shields.io/badge/puppeteer-40B5A4?style=flat-square&logo=puppeteer&logoColor=white)](https://developers.google.com/web/tools/puppeteer)
 [![React](https://img.shields.io/badge/React-61DAFB?style=flat-square&logo=React&logoColor=white)](https://developers.google.com/web/tools/puppeteer)
 
-
-
 # E-Campus 연동 확장 캘린더
 
 [E-Campus 연동 확장 캘린더](http://3.34.173.161:3001/)
@@ -32,6 +30,7 @@
 ## Getting Started (Installation)
 
 ### Set up
+
 ```sh
 git clone http://khuhub.khu.ac.kr/2021105636/Extended-Calendar.git
 npm install
@@ -40,12 +39,14 @@ npm install -g pm2
 ```
 
 Make `.env` in root directory.
+
 ```sh
 # MySQL
 DB_HOST=
 DB_USER=
 DB_PASSWORD=
 DB_DATABASE=
+DB_CONNECTION_LIMIT=
 
 # Express
 SERVER_IP=
@@ -58,38 +59,47 @@ REACT_APP_SERVER_IP=  # generally all the same
 Import `schema.sql` in your DB.
 
 ### Run to debug
+
 Terminal 1 ( Server )
+
 ```sh
 npm run server
 ```
+
 Terminal 2 ( React )
+
 ```sh
 npm start
 ```
 
 port : 3000
 <br>
+
 ### Run to deploy
+
 ```sh
 npm run build
 npm run pm2
 ```
+
 port : 3001
 <br>
 <br>
 
 ## Usage
+
 1. Enter your E-Campus ID and PW.
-<img src="/uploads/074a79ad560922af309e39b3186cbe2d/image.png" width="300" height="100">
+   <img src="/uploads/074a79ad560922af309e39b3186cbe2d/image.png" width="300" height="100">
 2. If the ID and password entered are correct, your ecampus information-based calendar will be created.
 3. Make sure that the courses you are taking are listed on the left and that your ecampus schedule reflects well.
 4. You can add a new schedule by clicking on the empty part of the calendar.
 5. You can view the schedule by day, week, and month.
 6. If you have finished checking the schedule, press the '로그아웃' button in the upper right corner.
 
-
 ## Contributing
+
 If you would like to add new features to this calendar, please follow these steps:
+
 1. Fork the Project
 2. Create your Feature Branch
 3. Commit your Changes

@@ -7,6 +7,7 @@ const poolOptions = {
   user: process.env.DB_USER,
   password: process.env.DB_PASSWORD,
   database: process.env.DB_DATABASE,
+  connectionLimit: process.env.DB_CONNECTION_LIMIT,
 };
 const pool = mysql2.createPool(poolOptions);