Adding postgres example

postgres/client.js

@@ -0,0 +1,17 @@
+const { Client } = require('pg')
+
+const pgclient = new Client({
+    host: 'postgres',
+    port: 5432,
+    user: 'postgres',
+    password: 'postgres',
+    database: 'postgres'
+});
+
+pgclient.connect();
+
+pgclient.query('SELECT NOW()', (err, res) => {
+    if (err) throw err
+    console.log(res)
+    pgclient.end()
+});