Anyone implement youtube api in unity

Anyone implement youtube api in unity ???
I implemented youtube api in unity
Following steps i follow to implement youtube api

  1. sign in using playgames services
  2. now i get server authentication code using playgames services
  3. After this i exchange server authentication code with token
  4. server returns token Without opening permission dialogue in unity so when i use http post request server says unauthorized request
    Anyone know how to open permission dialogue in unity??
    i already add permissions in android xml user_credential , get_accounts

Enabling YouTube API in the console and get Authcode by using play services For signing in to YouTube.
After Getting Authcode exchange it for token and finally we get login to YouTube in our game.