How to get refresh token for my application

[rahul3103]

Hey i am trying to access Google Drive via this app and I am trying to upload and list files. But I am facing issue when the access_token expires after an hour. from where should I get refresh_token.
Here is the repo: https://github.com/rahul3103/test_google_login

google.auth.exceptions.RefreshError
google.auth.exceptions.RefreshError: The credentials do not contain the necessary fields need to refresh the access token. You must specify refresh_token, token_uri, client_id, and client_secret.

Traceback (most recent call last)
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/flask/app.py", line 2309, in __call__
return self.wsgi_app(environ, start_response)
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/flask/app.py", line 2295, in wsgi_app
response = self.handle_exception(e)
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/flask/app.py", line 1741, in handle_exception
reraise(exc_type, exc_value, tb)
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
raise value
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/flask/app.py", line 2292, in wsgi_app
response = self.full_dispatch_request()
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/flask/app.py", line 1815, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/flask/app.py", line 1718, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
raise value
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/flask/app.py", line 1813, in full_dispatch_request
rv = self.dispatch_request()
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/flask/app.py", line 1799, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/Users/rahul/projects/personal/code/app.py", line 57, in home
fields="nextPageToken, files(id, name)"
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/googleapiclient/_helpers.py", line 130, in positional_wrapper
return wrapped(*args, **kwargs)
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/googleapiclient/http.py", line 835, in execute
method=str(self.method), body=self.body, headers=self.headers)
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/googleapiclient/http.py", line 162, in _retry_request
resp, content = http.request(uri, method, *args, **kwargs)
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/google_auth_httplib2.py", line 213, in request
self.credentials.refresh(self._request)
File "/Users/rahul/.virtualenvs/drive/lib/python3.6/site-packages/google/oauth2/credentials.py", line 129, in refresh
'The credentials do not contain the necessary fields need to '
google.auth.exceptions.RefreshError: The credentials do not contain the necessary fields need to refresh the access token. You must specify refresh_token, token_uri, client_id, and client_secret.