TypeError: Cann’t read properties of undefined (reading ‘then’)

// when I try to run then function on it, it will return this error

TypeError: Cannot read properties of undefined (reading ‘then’)
at Object.<anonymous> (/app/src/index.js:52:2)
at Module._compile (node:internal/modules/cjs/loader:1546:14)
at Module._extensions..js (node:internal/modules/cjs/loader:1691:10)
at Module.load (node:internal/modules/cjs/loader:1317:32)
at Module._load (node:internal/modules/cjs/loader:1127:12)
^

const  {Client} = require('pg');
    const PG_USER= 'root';
    const PG_PASSWORD = 'example';
    const PG_HOST= 'postgres';
    const PG_PORT='5432';
    const PG_URI= `postgresql://${PG_USER}:${PG_PASSWORD}@${PG_HOST}:${PG_PORT}`;

    const client =  new Client({
    connectionString: PG_URI,
    });
    client.connect(PG_URI)
    .then( () =>console.log('connect to postgresdb...'))
    .catch((err)=>console.log('failed connect to postgresdb:' ,err))