fix example: async/await createPool(conn), conn was missing

Author: szilveszter9

README.md

@@ -57,7 +57,7 @@ es7 async/await:
    let mysql = require('mysql2/promise');
    let conn = await mysql.createConnection({ database: test });
    let [rows, fields] = await conn.execute('select ?+? as sum', [2, 2]);
-   let pool = mysql.createPool();
+   let pool = mysql.createPool(conn);
    // execute in parallel, next console.log in 3 seconds
    await Promise.all([pool.query('select sleep(2)'), pool.query('select sleep(3)')]);
    console.log('3 seconds after');
@@ -105,7 +105,7 @@ var conn = mysql.createConnection({
         // continue handshake by sending response data
         // respond with error to propagate error to connect/changeUser handlers
         cb(null, response);
-      })      
+      })
     }
   }
 });