Use dockerfile alpine image

Dockerfile

@@ -1,5 +1,4 @@
-FROM golang:latest
-EXPOSE 42000
+FROM golang:alpine
 
 # Set go bin which doesn't appear to be set already.
 ENV GOPATH /go
@@ -7,13 +6,12 @@ ENV GOPATH /go
 ARG REPO_PATH=github.com/garritfra/blockchain-project
 
 # build directories
-RUN mkdir /app
-RUN mkdir -p /go/src/${REPO_PATH}
+RUN mkdir /app && mkdir -p /go/src/${REPO_PATH}
 ADD . /go/src/${REPO_PATH}
 WORKDIR /go/src/${REPO_PATH}
 
 # Build my app
-RUN go install
-RUN go build
+RUN go install && go build
+EXPOSE 42000
 CMD ["/go/bin/blockchain-project"]