Add multi stage docker build

Upgrade travis docker version

.travis.yml

@@ -1,11 +1,22 @@
-language: bash
-sudo: required
 dist: trusty
+sudo: required
+language: go
+
+services:  
+    - docker
 
 before_install:
 - echo "Testing Docker Hub credentials"
 - docker login -u=$DOCKER_USERNAME -p=$DOCKER_PASSWORD
 - echo "Docker Hub credentials are working"
+# If I see one day that Travis CI updates their default docker version
+# I can remove the lines below. That's why I leave this here :-)
+- docker version
+- sudo apt-get remove docker docker-engine docker.io
+- curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
+- sudo apt-get update
+- sudo apt-get install -y docker-ce
+- docker version
 
 install:
 - docker build -t cameradar .

Dockerfile

@@ -1,7 +1,8 @@
-FROM golang:alpine
-WORKDIR /go/src/github.com/EtixLabs/cameradar/cameraccess
+# Build stage
+FROM golang:alpine AS build-env
 
 COPY . /go/src/github.com/EtixLabs/cameradar
+WORKDIR /go/src/github.com/EtixLabs/cameradar/cameraccess
 
 RUN apk update && \
     apk upgrade && \
@@ -19,6 +20,14 @@ RUN go get github.com/jessevdk/go-flags
 RUN go get github.com/fatih/color
 RUN go get github.com/gernest/wow
 
-RUN go install
+RUN go build -o cameraccess
 
-ENTRYPOINT ["/go/bin/cameraccess"]
+# Final stage
+FROM alpine
+
+RUN apk --update add --no-cache nmap nmap-nselibs nmap-scripts \
+            curl-dev
+
+WORKDIR /app/cameraccess
+COPY --from=build-env /go/src/github.com/EtixLabs/cameradar/ /app/
+ENTRYPOINT ["/app/cameraccess/cameraccess"]