nginx-golang: add dev envs support (#273)

* Add Docker Desktop Developer Environments config
* Upgrade from Go 1.13 (🙀) to 1.18
* Rename `frontend` -> `proxy` for clarity & consistency
  with other samples
* Add Chi as a dependency to provide an example of Go
  module dependencies for parity with other samples

Signed-off-by: Milas Bowman <milas.bowman@docker.com>

nginx-golang/README.md

@@ -1,5 +1,5 @@
 ## Compose sample application
-### NGINX proxy with GO backend
+### NGINX proxy with Go backend
 
 Project structure:
 ```
@@ -8,25 +8,32 @@ Project structure:
 │   ├── Dockerfile
 │   └── main.go
 ├── compose.yaml
-├── frontend
-│   ├── Dockerfile
+├── proxy
 │   └── nginx.conf
 └── README.md
 ```
 
-[_compose.yaml_](compose.yaml)
+[`compose.yaml`](compose.yaml)
 ```
 services:
-  frontend:
-    build: frontend
+  proxy:
+    image: nginx
+    volumes:
+      - type: bind
+        source: ./proxy/nginx.conf
+        target: /etc/nginx/conf.d/default.conf
+        read_only: true
     ports:
       - 80:80
     depends_on:
       - backend
+
   backend:
-    build: backend
+    build:
+      context: backend
+      target: builder
 ```
-The compose file defines an application with two services `frontend` and `backend`.
+The compose file defines an application with two services `proxy` and `backend`.
 When deploying the application, docker compose maps port 80 of the frontend service container to the same port of the host as specified in the file.
 Make sure port 80 on the host is not already in use.
 
@@ -40,20 +47,19 @@ Step 1/7 : FROM golang:1.13 AS build
 1.13: Pulling from library/golang
 ...
 Successfully built 4b24f27138cc
-Successfully tagged nginx-golang_frontend:latest
-WARNING: Image for service frontend was built because it did not already exist. To rebuild this image you must use `docker-compose build` or `docker-compose up --build`.
+Successfully tagged nginx-golang_proxy:latest
 Creating nginx-golang_backend_1 ... done
-Creating nginx-golang_frontend_1 ... done
+Creating nginx-golang_proxy_1 ... done
 ```
 
 ## Expected result
 
 Listing containers must show two containers running and the port mapping as below:
 ```
-$ docker ps
-CONTAINER ID        IMAGE                   COMMAND                  CREATED             STATUS              PORTS                  NAMES
-8bd5b0d78e73        nginx-golang_frontend   "nginx -g 'daemon of…"   53 seconds ago      Up 52 seconds       0.0.0.0:80->80/tcp     nginx-golang_frontend_1
-56f929c240a0        nginx-golang_backend    "/usr/local/bin/back…"   53 seconds ago      Up 53 seconds                              nginx-golang_backend_1
+$ docker compose ps
+NAME                     COMMAND                  SERVICE             STATUS              PORTS
+nginx-golang-backend-1   "/code/bin/backend"      backend             running
+nginx-golang-proxy-1     "/docker-entrypoint.…"   proxy               running             0.0.0.0:80->80/tcp
 ```
 
 After the application starts, navigate to `http://localhost:80` in your web browser or run:
@@ -77,3 +83,14 @@ Stop and remove the containers
 ```
 $ docker compose down
 ```
+
+## Use with Docker Development Environments
+
+You can use this sample with the Dev Environments feature of Docker Desktop.
+
+![Screenshot of creating a Dev Environment in Docker Desktop](../dev-envs.png)
+
+To develop directly on the services inside containers, use the HTTPS Git url of the sample:
+```
+https://github.com/docker/awesome-compose/tree/master/nginx-golang
+```