Creating signature hmac-sha1 in rails for magento integration

So I'm trying to create a signature to access Magento APIs via Integration but I don't get a valid oauth signature (Magento uses oauth1).

On using the same timestamp and nonce in postman I get the proper oauth signature. Why doesn't this produce a signature equivalent to that?

hmac=OpenSSL::HMAC.digest('sha1',secret_key, base_string)
signature = Base64 encode64(hmac) 

The base string:

        oauth_consumer_key=params[:oauth_consumer_key]
        oauth_signature_method='HMAC-SHA1'
        oauth_nonce=Random.rand(100000).to_s
        oauth_timestamp=Time.now.to_i.to_s
        oauth_version='1.0'
        parameters ='oauth_consumer_key=' +
              oauth_consumer_key +
              '&oauth_nonce=' +
              oauth_nonce +
              '&oauth_signature_method=' +
              oauth_signature_method +
              '&oauth_timestamp=' +
              oauth_timestamp +
              '&oauth_version=' +
              oauth_version
        url = "http://localhost/demowebsite/oauth/token/request"
        base_string = 'POST&' +CGI.escape(url) + '&' + CGI.escape(parameters)
        #as I have no token yet
        secret_key = oauth_consumer_secret +'&'+'' 
 #POST&http%3A%2F%2Flocalhost%2Fdemowebsite%2Foauth%2Ftoken%2Frequest&oauth_consumer_key%3Dqv4w11m4o5f8vqx2uhfzovrc6veevg5u%26oauth_nonce%3D94770%26oauth_signature_method%3DHMAC-SHA1%26oauth_timestamp%3D1591680691%26oauth_version%3D1.0

Thanks in advance

Usually the base_string is the culprit. If you put the sample base string here, I can help you further