Have just implemented this for a project im working on.
So for LIKE, I'm using GraphQL Mutation. You need two argument.userId, postId
Then ensure the user is authenticated and first know for sure the post exist and then do something like post.createLike(user) depending on how you structured your DB and table. If you need further help on this, do let me know.
For removeLike its almost similar, post.removeLike(user)