Setup is based on clojurescript getting started guide. I've added a require statement to the core ns and using the latest master sha
deps.edn
{:deps {org.clojure/clojurescript {:git/url "https://github.com/clojure/clojurescript.git"
:sha "ec0fc33030ae1858a29c52f38e81fba4180d492b"}}}
src/hello_world/core.cljs