LDAP JS auth getting error

i am new to ldap. i am using ldapauth.js to authenticate the credentials.

i have used ldapauth npm for authentucation.

/*--------------LDAP_AUTH--------------*/

var ldap = require('ldapjs');
var LdapAuth = require('ldapauth');
var server = ldap.createServer();

server.search('o=example', function(req, res, next) {
  var obj = {
    dn: req.dn.toString(),
    attributes: {
      objectclass: ['organization', 'top'],
      o: 'example'
    }
  };

  if (req.filter.matches(obj.attributes))
    res.send(obj);

  res.end();
});

server.listen(1389, function() {
  console.log('LDAP server listening at %s', server.url);
});



var options = {
    url: "ldap://0.0.0.0:1389",
    adminDn: "uid=myadminusername,ou=users,o=example",
    adminPassword: "mypassword",
    searchBase: "ou=users,o=example",
    searchFilter: "(uid={{username}})"
};
var auth = new LdapAuth(options);

auth.authenticate('myadminusername', 'mypassword', function(err, user) { console.log('err'); 
    console.log(err);
console.log(err.message);
console.log('user');
console.log(user);
});

auth.close(function(err) { console.log('errorr'); })

in the console i am getting the error message.

LDAP server listening at ldap://0.0.0.0:1389
err
{ dn: [Getter],
  code: [Getter],
  name: [Getter],
  message: [Getter] }
No tree found for: uid=myadminusername, ou=users, o=example
user
undefined

Please help me in figuring out what is wrong.

Thanks for your time