Omniauth and google oauth2 error without Devise - Rails 4

Hey guys so i am trying to implement social authentications but i am stuck.

I've setup correctly the callback url both in my routes and google console and i've verified it by displaying the auth_hash in browser.

my session_controller.rb

def google_oauth2
    begin
    auth_hash = request.env['omniauth.auth']
    @user = User.from_omniauth(auth_hash)
    if @user
      session[:user_id] = @user.id
      flash[:success] = "Welcome, #{@user.name}!"
      redirect_to root_path
    else
      user.uid = auth_hash['uid']
      user.provider = auth_hash['provider']
      user.name = auth_hash['info']['name']
      user.email = auth_hash['info']['email']
      user.image_url = auth_hash['info']['image']

      @user = User.new(name: user.name,email: user.email, provider: user.provider,uid: user.uid,image_url: image_url)
      @user.save!
      flash[:success] = "Welcome, #{@user.name}!You've signed up!"
    end
    rescue
      flash[:warning] = "There was an error while trying to authenticate you..."
    end
    redirect_to root_path
  end

user.model

def self.from_omniauth(auth_hash)
      user = find_by(uid: auth_hash['uid'], provider: auth_hash['provider'])
      user
end

And this is the error in console

Started GET "/auth/google_oauth2/callback?state=a85d28b3b8d112171450ab3cafd47216937847a5747c08f4&code=4/H37yKnP8xbG_d2DEwS55WyAUXTlhBRlliREvGzZhD9s" for ::1 at 2015-08-06 19:13:02 +0300
I, [2015-08-06T19:13:02.114803 #5401]  INFO -- omniauth: (google_oauth2) Callback phase initiated.
Processing by SessionsController#google_oauth2 as HTML
  Parameters: {"state"=>"a85d28b3b8d112171450ab3cafd47216937847a5747c08f4", "code"=>"4/H37yKnP8xbG_d2DEwS55WyAUXTlhBRlliREvGzZhD9s", "provider"=>"google_oauth2"}
  User Load (0.1ms)  SELECT  "users".* FROM "users" WHERE "users"."uid" = ? AND "users"."provider" = ? LIMIT 1  [["uid", "118084345864130537689"], ["provider", "google_oauth2"]]
Redirected to http://localhost:3000/
Completed 302 Found in 9ms (ActiveRecord: 0.6ms)

The problem is that the error in my session controller fires each time,and no user is created

"There was an error while trying to authenticate you..."

Anyone who can collaborate?