multistage build

Dockerfile

@@ -1,15 +1,12 @@
-FROM alpine:3.8
-
-ENV GOPATH=/go
-
+FROM golang:alpine AS build
 WORKDIR /go/src/app
 COPY . /go/src/app/
+RUN apk --no-cache add git gcc musl-dev &&\
+ go get ./... &&\
+ go test -v &&\
+ CGO_ENABLED=0 go build -o /ssh-key-manager .
 
-RUN apk --no-cache add ca-certificates go git musl-dev \
-  && go get ./... \
-  && go test -v \
-  && CGO_ENABLED=0 go build -o /ssh-key-manager . \
-  && apk del go git musl-dev \
-  && rm -rf $GOPATH
-
+FROM alpine:3.8
+RUN apk add --no-cache ca-certificates
+COPY --from=build /ssh-key-manager /ssh-key-manager
 CMD [ "/ssh-key-manager" ]