home_controller.rb

class HomeController < ApplicationController

  def index
    @data = session[:omniauth_data]
  end
end

index.html.erb

<%= @data %>

omniauth_callback_controller.rb

class OmniauthCallbacksController < Devise::OmniauthCallbacksController
  def providers
    user = User.from_omniauth(request.env["omniauth.auth"])
    if user.persisted?
      flash[:notice] = I18n.t "devise.omniauth_callbacks.success", :kind => "Google"
      User.data_from_omniauth(request.env["omniauth.auth"])  # This will have a api data, for testing i am just passing the auth and also using User model 
      
      session[:omniauth_data] = user # set session data during callback
      
      sign_in_and_redirect user
    else
      session["devise.user_attributes"] = user.attributes
      redirect_to new_user_registration_url
    end
  end
  alias_method :google_oauth2, :providers

  # def failure

  # end
end

user.rb

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable, :confirmable,
         :recoverable, :rememberable, :trackable, :validatable, :omniauthable, :omniauth_providers => [:google_oauth2]

  def self.from_omniauth(auth)
    where(auth.slice(:provider, :uid)).first_or_create do |user|
      user.provider = auth.provider
      user.uid = auth.uid
    end
  end

  def self.new_with_session(params, session)
    if session["devise.user_attributes"]
      new session["devise.user_attributes"] do |user|
        user.attributes = params
        user.valid?
      end
    else
      super
    end
  end

  def self.data_from_omniauth(data) # This is the method i am passing data
    # parse data here
    # return information to be passed to controller/view
    print Rails.logger.info "::USER-DATA::#{data}"
  end

  def password_required?
    super && provider.blank?
  end

  def update_with_password(params, *options)
    if encrypted_password.blank?
      update_attributes(params, *options)
    else
      super
    end
  end

  def confirmation_required?
    super && provider.blank?
  end
end