nginx - map directive in supplementary conf file along with invocation

files/nginx/Dockerfile

@@ -1,3 +1,3 @@
 FROM nginx:latest
 
-RUN sed -i 's/\#gzip.*on;/server_tokens\toff;\n    # Set the `immutable` cache control options only for assets with a cache busting `v` argument\n    map $arg_v $asset_immutable {\n        "" "";\n    default ", immutable";\n\n    }\n    #gzip\ton;/' /etc/nginx/nginx.conf
+RUN sed -i 's/\#gzip.*on;/server_tokens\toff;\n    #gzip\ton;/' /etc/nginx/nginx.conf

templates/default.conf.j2

@@ -3,6 +3,11 @@
         server 127.0.0.1:9000;
     }
 
+    map $arg_v $asset_immutable {
+        "" "";
+    default ", immutable";
+    }
+
     server {
         listen 8080;