hello.go

// Copyright 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package main

import (
	"fmt"
	"html/template"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"regexp"
)

type Data struct {
	Service      string
	Revision     string
	Project      string
	Region       string
}

func main() {
	tmpl := template.Must(template.ParseFiles("index.html"))

	// Get project ID from metadata server
	project := ""
	client := &http.Client{}
	req, _ := http.NewRequest("GET", "http://metadata.google.internal/computeMetadata/v1/project/project-id", nil)
	req.Header.Set("Metadata-Flavor", "Google")
	res, err := client.Do(req)
	if err == nil {
		defer res.Body.Close()
		if res.StatusCode == 200 {
			responseBody, err := ioutil.ReadAll(res.Body)
			if err != nil {
				log.Fatal(err)
			}
			project = string(responseBody)
		}
	}

	// Get region from metadata server
	region := ""
	req, _ = http.NewRequest("GET", "http://metadata.google.internal/computeMetadata/v1/instance/region", nil)
	req.Header.Set("Metadata-Flavor", "Google")
	res, err = client.Do(req)
	if err == nil {
		defer res.Body.Close()
		if res.StatusCode == 200 {
			responseBody, err := ioutil.ReadAll(res.Body)
			if err != nil {
				log.Fatal(err)
			}
			region = regexp.MustCompile(`projects/[^/]*/regions/`).ReplaceAllString(string(responseBody), "")
		}
	}

	service := os.Getenv("K_SERVICE")
	revision := os.Getenv("K_REVISION")

	data := Data{
		Service:      service,
		Revision:     revision,
		Project:      project,
		Region:       region,
	}

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		tmpl.Execute(w, data)
	})

	fs := http.FileServer(http.Dir("./assets"))
	http.Handle("/assets/", http.StripPrefix("/assets/", fs))

	port := os.Getenv("PORT")
	if port == "" {
		port = "8080"
	}

	log.Print("Hello from Cloud Run! The container started successfully and is listening for HTTP requests on $PORT")
	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%s", port), nil))
}