Use promu for dockerized builds

Dockerfile.build.amd64.glibc

 FROM amd64/golang:stretch
 
+RUN go get -u github.com/prometheus/promu
 COPY . /go/src/github.com/mitchellrj/hue_exporter
 WORKDIR /go/src/github.com/mitchellrj/hue_exporter
 
 VOLUME /build
-CMD go build -o /build/hue_exporter.amd64
+CMD promu build && mv hue_exporter /build/hue_exporter.amd64

Dockerfile.build.amd64.musl

 FROM amd64/golang:alpine
 
+RUN go get -u github.com/prometheus/promu
 COPY . /go/src/github.com/mitchellrj/hue_exporter
 WORKDIR /go/src/github.com/mitchellrj/hue_exporter
 
 VOLUME /build
-CMD go build -o /build/hue_exporter.amd64.musl
+CMD promu build && mv hue_exporter /build/hue_exporter.amd64.musl

Dockerfile.build.arm7.glibc

 FROM arm32v7/golang:stretch
 
+RUN go get -u github.com/prometheus/promu
 COPY . /go/src/github.com/mitchellrj/hue_exporter
 WORKDIR /go/src/github.com/mitchellrj/hue_exporter
 
 VOLUME /build
-CMD go build -o /build/hue_exporter.arm7
+CMD promu build && mv hue_exporter /build/hue_exporter.arm7

Dockerfile.build.arm7.musl

@@ -2,8 +2,9 @@ FROM armhf/alpine:latest
 
 RUN apk add --no-cache git go musl-dev && mkdir /go
 ENV GOPATH=/go
+RUN go get -u github.com/prometheus/promu
 COPY . /go/src/github.com/mitchellrj/hue_exporter
 WORKDIR /go/src/github.com/mitchellrj/hue_exporter
 
 VOLUME /build
-CMD go build -o /build/hue_exporter.arm7.musl
+CMD promu build && mv hue_exporter /build/hue_exporter.arm7.musl

Makefile

@@ -54,4 +54,5 @@ push:
 	docker push mitchellrj/hue_exporter:latest-arm7
 	docker push mitchellrj/hue_exporter:$$(build/hue_exporter.darwin -V)-arm7
 
+DEFAULT: all
 .PHONY: all style test format vet staticcheck promu build