I used Google Cloud Platform App Engine and Google Cloud SQL, Sequelize, but Error: connect ETIMEDOUT error - express

Question

The server is intended to be deployed via GCP, React is deployed as a separate instance.
I use Sequelize, Node, Express, MySQL.
Cloud SQL confirmed that Sequelize and DB were well linked through workbench.
I once distributed it through APP Engine, so I added Cloud SQL-related settings, and if there was no problem, I decided that it would be possible to call the desired data.
The deployment was successful through gcloud app deployment and tried to verify that the desired API was called well, but 500 errors were constantly occurring.
I don't know where to fix it, can you give me a tip?
config/config.js
require('dotenv').config();
module.exports = {
development: {
username: "root",
password: process.env.SEQUELIZE_PASSWORD,
database: "DBName",
host: "SQL Instance Public IP Address",
dialect: "mysql",
timezone: "+09:00"
},
test: {
username: "root",
password: null,
database: "database_test",
host: "127.0.0.1",
dialect: "mysql"
},
production: {
username: "root",
password: process.env.SEQUELIZE_PASSWORD,
database: "DBName",
host: "SQL Instance Public IP Address",
dialect: "mysql",
timezone: "+09:00",
logging: false
},
}
server.js
const express = require('express')
const cors = require('cors')
const dotenv = require('dotenv')
const Test = require('./Routes/Test')
const { sequelize } = require('./models')
dotenv.config()
const app = express()
app.set("PORT", process.env.PORT || 8080)
sequelize.sync({force: false})
.then(() => {console.log('db Oneline')})
.catch((err) => {console.error(err)})
app.use(cors({origin: "*"}))
app.use(express.json())
app.use('/test',Test)
app.listen(app.get('PORT'), () => {
console.log(app.get("PORT"), 'Online')
})
In server.js, /test aims to receive this data from the front desk in a get request.
app.yaml
runtime: nodejs
env: flex
service: default
manual_scaling:
instances: 1
resources:
cpu: 1
memory_gb: 0.5
disk_size_gb: 10
env_variables:
SQL_USER: "root"
SQL_PASSWORD: "root password entered when SQL was created"
SQL_DATABASE: "Instance ID"
INSTANCE_CONNECTION_NAME: "logintest-b314a:asia-northeast3:Instance ID"
beta_settings:
cloud_sql_instances: "logintest-b314a:asia-northeast3:Instance ID"
Error Messages from Error Reporting
SequelizeConnectionError: connect ETIMEDOUT
at ConnectionManager.connect (/app/node_modules/sequelize/lib/dialects/mysql/connection-manager.js:102:17)
at processTicksAndRejections (internal/process/task_queues.js:97:5)
parent: Error: connect ETIMEDOUT
at Connection._handleTimeoutError (/app/node_modules/mysql2/lib/connection.js:189:17)
at listOnTimeout (internal/timers.js:554:17)
at processTimers (internal/timers.js:497:7) {