Include the version in the initial log output

Signed-off-by: Marcus Noble <github@marcusnoble.co.uk>

.github/workflows/docker.yaml

@@ -37,3 +37,5 @@ jobs:
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          build-args:
+            VERSION: ${{ steps.meta.outputs.version }}

Dockerfile

@@ -4,6 +4,7 @@ ARG TARGETPLATFORM
 ARG BUILDPLATFORM
 ARG TARGETOS
 ARG TARGETARCH
+ARG VERSION="dev"
 
 RUN apk update && apk add -U --no-cache ca-certificates
 
@@ -12,7 +13,7 @@ ADD go.mod go.sum ./
 RUN go mod download
 ADD main.go .
 ADD pkg/ ./pkg
-RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -ldflags="-w -s" -o tailscale-exporter main.go
+RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -ldflags="-w -s -X 'main.Version=${VERSION}'" -o tailscale-exporter main.go
 
 FROM --platform=${TARGETPLATFORM:-linux/amd64} scratch
 WORKDIR /app/

main.go

@@ -11,6 +11,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
+var Version = "dev"
 var addr string
 
 func init() {
@@ -32,7 +33,7 @@ func main() {
 	metrics.Collect(client, reg)
 
 	http.Handle("/metrics", promhttp.HandlerFor(reg, promhttp.HandlerOpts{Registry: reg}))
-	log.Printf("tailscale-exporter")
+	log.Printf("tailscale-exporter - %s", Version)
 	log.Printf("Listening on %s", addr)
 	log.Fatal(http.ListenAndServe(addr, nil))
 }