Error: connect ENOENT /cloudsql/<my project id>:asia-south1:<my database instance name>

runtime: nodejs
env: flex

manual_scaling:
  instances: 1
resources:
  cpu: 1
  memory_gb: 0.5
  disk_size_gb: 10

env_variables:
  ST_ENV: 'Production' //Used to set the app listening on the below port
  ST_PORT: '8080'
  SQL_USER: '<username>'
  SQL_PASSWORD: '<password>'
  SQL_DATABASE: '<databasename>'
  INSTANCE_CONNECTION_NAME: '/cloudsql/<my project id>:asia-south1:<my database instance name>'

  beta_settings:
  cloud_sql_instances: '<my project id>:asia-south1:<my database instance name>'

database: {
            connectionLimit: 10,
            // host     : process.env.INSTANCE_CONNECTION_NAME,
            socketPath: process.env.INSTANCE_CONNECTION_NAME,
            user     : process.env.SQL_USER,
            password : process.env.SQL_PASSWORD,
            database : process.env.SQL_DATABASE,
            multipleStatements : true

        }

var db = config.production.database;
var pool = mysql.createPool(db);

Error: connect ECONNREFUSED 127.0.0.1:3306'