gistfile1.txt

      def self.oauth_client
        OAuth2::Client.new(
          AppConfig.slack_api_client.client_id,
          AppConfig.slack_api_client.client_secret,
          site: 'https://slack.com',
          authorize_url: '/oauth/authorize',
          token_url: '/api/oauth.access',
        )
      end

        oauth_token = oauth_client.auth_code.get_token(
          code,
          redirect_uri: redirect_uri,
          headers: {'Authorization' => AUTHORIZATION_HEADER}
        )
        
        access_token = oauth_token.token 
        params = oauth_token.params 
        
        # In my code I was just getting params which dont have access-token as the library deletes it while setting the params.