Improvements on Dockerfile and deploy

Dockerfile

@@ -0,0 +1,12 @@
+FROM golang:1.12 as build
+WORKDIR /app
+ADD . .
+RUN GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -ldflags="-w -s" -mod vendor
+
+FROM alpine
+COPY --from=build /app/gocity /bin/gocity
+
+RUN apk update && apk upgrade && \
+    apk add --no-cache bash git openssh
+
+CMD ["/bin/gocity", "server"]

Makefile

@@ -21,4 +21,5 @@ build-docker:
 	docker build -t rodrigobrito/gocity -f ./server/docker/Dockerfile .
 
 deploy:
-	cd server && we deploy -p rodrigo
+	heroku container:push -a go-city web
+	heroku container:release -a go-city web

README.md

@@ -10,6 +10,9 @@
 <hr />
 
 Available here: https://go-city.github.io
+
+Tool Paper: [26th International Conference on Software Analysis, Evolution and Reengineering (SANER)](https://ieeexplore.ieee.org/document/8668008)
+<br>PDF Version: [ASERG Page](https://homepages.dcc.ufmg.br/~mtov/pub/2019-saner-gocity.pdf)
 
 GoCity is an implementation of the Code City metaphor for visualizing source code. GoCity represents a Go program as a city, as follows: 
 

main.go

@@ -34,9 +34,10 @@ func main() {
 			Description: "Start a local server to analyze projects",
 			Flags: []cli.Flag{
 				cli.IntFlag{
-					Name:  "port",
-					Value: defaultPort,
-					Usage: "Local server port",
+					Name:   "port",
+					Value:  defaultPort,
+					Usage:  "Local server port",
+					EnvVar: "PORT",
 				},
 			},
 			Action: func(c *cli.Context) error {