NodeJS: Unhandled promise rejection

I'm having a little problem and after debugged all the app I noticed that this is the file that's causing the problem, returning me a UnhandledPromiseRejection

'use strict'

const connection = require('../models/'),
      oracledb   = require('oracledb'),
      conexion   = oracledb.getConnection(connection)
oracledb.outFormat = oracledb.OBJECT;

module.exports  = {
  index(req, res) {
  conexion.then(con => {
    return con.execute(
      `SELECT id_application, name, description, creation_date ` +
      `FROM application `
    ).then(bucket => {
      return con.execute(
        `SELECT id_definition, id_application, field_name_original, field_name_new,
        column_name, position, id_type_data, field_size, creation_date,
        description, filter, visible ` +
        `FROM definition `
      ).then(definitions => {
        res.status(200).json(creaJSON(bucket, definitions))
      }).catch(error  => { return res.status(500).json({'message': error}) })
    }).catch(err  =>  { return res.status(500).json({'message': err}) })
  }).catch(err  =>  { return res.status(500).json({'message': err}) })
  },
  create(req, res)  {
  },
  update(req, res)  {
  }
}

const doRelease = (connection) => {
  connection.close((err)  =>  {
    if(err) console.error(err.message);
  })
}

const creaJSON = (buckets, definitions)  => {
  var df = new Array()
  buckets['rows'].map(obj =>  {
    definitions['rows'].map(def =>  {
      if(obj['ID_APPLICATION'] == def['ID_APPLICATION']) df.push(def)
    })
    obj['Definitions'] = df
    df = []
  })
  return buckets.rows
}

after the UnhandledPromiseRejection is being followed by: Error: ORA-12170: TNS:Connect timeout occurred

(node:1270) DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.JS process with a non-zero exit code.

I already looked for solutions, some says that promises are not catching correctly but I don't see any problem with them. Any other suggestion?

Any help will be welcome.

Thanks

via CanKer DiAlike