use the same go version as production

Dockerfile

@@ -1,12 +1,12 @@
-FROM golang
+FROM golang:1.9.4
 
 RUN go get -u github.com/golang/dep/cmd/dep
 
-COPY Gopkg.toml Gopkg.lock /go/src/github.com/heroku/herald/
 WORKDIR /go/src/github.com/heroku/herald/
+COPY Gopkg.toml Gopkg.lock ./
 RUN dep ensure --vendor-only
 
-COPY ./ /go/src/github.com/heroku/herald/
+COPY ./ ./
 
 RUN go build
 

Makefile

@@ -1,5 +1,5 @@
 test:
-	go run cmd/herald-test/main.go
+	go test
 run:
 	go run cmd/version-scraper/main.go