Fix Dockerfile to build Go application with correct module setup and port configuration.

guestbook-go/Dockerfile

@@ -12,17 +12,27 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM golang:1.10.0
+FROM golang:1.18 AS builder
+
+
+WORKDIR /app
+
+
+RUN go mod init temp-module || true
 RUN go get github.com/codegangsta/negroni \
            github.com/gorilla/mux \
            github.com/xyproto/simpleredis/v2
-WORKDIR /app
-ADD ./main.go .
+
+
+COPY ./main.go .
+
+
 RUN CGO_ENABLED=0 GOOS=linux go build -o main .
 
+
 FROM scratch
 WORKDIR /app
-COPY --from=0 /app/main .
+COPY --from=builder /app/main .
 COPY ./public/index.html public/index.html
 COPY ./public/script.js public/script.js
 COPY ./public/style.css public/style.css