const [upvotePost, { error, loading, data }] = useMutation(UPVOTE_POST, {
    variables: { postId: props.post.id, userId: loggedUserId },
    refetchQueries: [{ query: POSTS_LIST }]
});

if (error) {
    error.graphQLErrors.map(error => {
      console.log(error);
      if (error.extensions.code === "constraint-violation")
        toast(`${error.message}`);
    });
}