Try building with correct build base.

Dockerfile

@@ -1,8 +1,13 @@
+FROM golang:alpine AS build
+MAINTAINER chris
+RUN apk add git --no-cache && \
+    git clone https://github.com/mdlayher/apcupsd_exporter /tmp/build && \
+    cd /tmp/build && \
+    go build -o /go/bin/apcupsd_exporter /tmp/build/cmd/apcupsd_exporter/main.go
+
 FROM alpine:latest
-
 RUN apk update && apk upgrade && apk add --no-cache libusb apcupsd
-
 COPY apc-deamon.conf /etc/apcupsd/apcupsd.conf
-EXPOSE 3551/tcp 3551/udp
-
-ENTRYPOINT /sbin/apcupsd -b
+COPY --from=build /go/bin/apcupsd_exporter /sbin/apcupsd_exporter
+EXPOSE 9162 3551/tcp 3551/udp
+ENTRYPOINT /sbin/apcupsd -b && /sbin/apcupsd_exporter -apcupsd.addr localhost:3551