Add heartbeat endpoint and improve dockerfile

Dockerfile

@@ -1,19 +1,17 @@
 FROM golang:1.16-alpine3.13 as build
 RUN apk add --no-cache git gcc musl-dev sqlite-dev
-ADD *.go /app/
-ADD go.mod /app/
-ADD go.sum /app/
 WORKDIR /app
+ADD *.go go.mod go.sum /app/
 RUN go build --tags "libsqlite3 linux sqlite_fts5"
 
 FROM alpine:3.13
 RUN apk add --no-cache sqlite-dev tzdata tor
 COPY templates/ /app/templates/
-COPY --from=build /app/GoBlog /bin/
 WORKDIR /app
 VOLUME /app/config
 VOLUME /app/data
 EXPOSE 80
 EXPOSE 443
 EXPOSE 8080
-CMD ["GoBlog"]
+CMD ["GoBlog"]
+COPY --from=build /app/GoBlog /bin/

http.go

@@ -50,6 +50,7 @@ func startServer() (err error) {
 		finalHandler = securityHeaders(finalHandler)
 	}
 	finalHandler = servertiming.Middleware(finalHandler, nil)
+	finalHandler = middleware.Heartbeat("/ping")(finalHandler)
 	finalHandler = middleware.Compress(flate.DefaultCompression)(finalHandler)
 	finalHandler = middleware.Recoverer(finalHandler)
 	if appConfig.Server.Logging {