The code you have written is not a BFS, but actually a DFS. This is because after you visit a node, you push its neighbors into the front of the queue, when you should push it onto the back of the queue. Remember: going to the front is cutting the queue!
More importantly, your code also doesn’t handle the case when you do revisit a node. Say you go from A → B → A. Then your search function just returns nothing.
Also, you should add a case to handle if the target node is missing. Maybe return an :error
A suggestion, you can also make the visited data structure a MapSet, that way you can use the in-built data functions to test if a node has been visited:
