upd

langs/scala/Dockerfile.user

@@ -1,4 +1,5 @@
 RUN curl -fL https://github.com/coursier/coursier/releases/latest/download/cs-x86_64-pc-linux.gz | gzip -d > cs && chmod +x cs 
 RUN yes | ./cs setup
+RUN yes | ./cs install scala:2.12.15 scalac:2.12.15
 RUN rm ./cs
 ENV PATH="${PATH}:/home/user/.local/share/coursier/bin"

langs/scala/run.sh

@@ -2,4 +2,4 @@ IN="$(mktemp --suffix .sc)"
 
 cat > "$IN"
 
-scala "$IN"
+scala run "$IN"