Magento 2 oauth 1 get request token - magento

Question

Am not able to get request token in magento app. Signature is always invalid.
This is the code i use to generate the signature. The consumer key is the one is i get from localhost:8000 (magento shop) request to localhost:3000.
I tried changing the url both to localhost 8000 and 3000.
Followed these instructions: Magento instructions
function getSignature($consumerKey)
{
$params = array(
'oauth_nonce' => uniqid(mt_rand(1, 1000)),
'oauth_signature_method' => 'HMAC-SHA1',
'oauth_timestamp' => time(),
'oauth_version' => '1.0',
'oauth_consumer_key' => $consumerKey,
);
ksort($params);
$baseString = strtoupper('POST') . '&';
$baseString .= rawurlencode('http://localhost:8000') . '&';
$baseString .= rawurlencode(buildSignatureDataString($params));
$signature = hash_hmac('SHA1', $baseString, getSigningKey(), true);
return base64_encode($signature);
}
function getSigningKey()
{
return rawurlencode('magento_private_key') . '&';
}
function buildSignatureDataString(array $signatureData)
{
$signatureString = '';
$delimiter = '';
foreach ($signatureData as $key => $value) {
$signatureString .= $delimiter . $key . '=' . $value;
$delimiter = '&';
}
return $signatureString;
}