Cleaning up the Dockerfile

.dockerignore

@@ -0,0 +1,4 @@
+# Created by .ignore support plugin (hsz.mobi)
+.idea/
+*.iml
+.git/

Dockerfile

@@ -2,8 +2,8 @@
 FROM golang:1.13 as builder
 
 # Add the project in the image
-ADD . /go/src/github.com/kumina/postfix_exporter
-WORKDIR /go/src/github.com/kumina/postfix_exporter
+ADD . /build
+WORKDIR /build
 
 # Install needed dependencies for the build
 RUN apt-get update -q && apt-get install -qy \
@@ -21,6 +21,6 @@ EXPOSE 9154
 WORKDIR /
 
 # Copy the binary from the build image to the real one
-COPY --from=builder /go/src/github.com/kumina/postfix_exporter/postfix_exporter .
+COPY --from=builder /build/postfix_exporter .
 
 ENTRYPOINT ["/postfix_exporter"]