Quickstart: Build and deploy a Go web app to Cloud Run

Write the sample application

To write an application in Go:

1. Create a new directory named helloworld and change directory into it:

   mkdir helloworld
   cd helloworld
   

2. Initialize a go.mod file from the project directory to declare the go module:

   go mod init github.com/GoogleCloudPlatform/golang-samples/run/helloworld
   

3. Create a new file named main.go and paste the following code into it:

   
   // Sample run-helloworld is a minimal Cloud Run service.
   package main
   
   import (
   	"fmt"
   	"log"
   	"net/http"
   	"os"
   )
   
   func main() {
   	log.Print("starting server...")
   	http.HandleFunc("/", handler)
   
   	// Determine port for HTTP service.
   	port := os.Getenv("PORT")
   	if port == "" {
   		port = "8080"
   		log.Printf("defaulting to port %s", port)
   	}
   
   	// Start HTTP server.
   	log.Printf("listening on port %s", port)
   	if err := http.ListenAndServe(":"+port, nil); err != nil {
   		log.Fatal(err)
   	}
   }
   
   func handler(w http.ResponseWriter, r *http.Request) {
   	name := os.Getenv("NAME")
   	if name == "" {
   		name = "World"
   	}
   	fmt.Fprintf(w, "Hello %s!\n", name)
   }
   

   This code creates a basic web server that listens on the port defined by the PORT environment variable.

Your app is finished and ready to be deployed.

Deploy to Cloud Run from source

Important: This quickstart assumes that you have owner or editor roles in the project you are using for the quickstart. Otherwise, refer to the Cloud Run Source Developer role for the required permissions for deploying a Cloud Run resource from source.

Deploy from source automatically builds a container image from source code and deploys it.

To deploy from source:

1. In your source code directory, deploy the current folder using the following command:

   gcloud run deploy --source .

   1. When you are prompted for the service name, press Enter to accept the default name, for example helloworld.

   2. If you are prompted to enable additional APIs on the project, for example, the Artifact Registry API, respond by pressing y.

   3. When you are prompted for region: select the region of your choice, for example us-central1.

   4. If you are prompted to create a repository in the specified region, respond by pressing y.

   5. If you are prompted to allow unauthenticated invocations: respond y. You might not see this prompt if there is a domain restriction organization policy that prevents it; for more details see the Before you begin section.

   Then wait a few moments until the deployment is complete. On success, the command line displays the service URL.

2. Visit your deployed service by opening the service URL in a web browser.

Congratulations! You have just deployed a container image from source code to Cloud Run. Cloud Run automatically and horizontally scales out your container image to handle the received requests, then scales in when demand decreases. You only pay for the CPU, memory, and networking consumed during request handling.