Create HelloWorld HTTP Cloud Function
Create Gopher HTTP Cloud Function
HTTP Google Cloud Functions in Go
Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.
Cloud Functions is an event-driven serverless compute platform. Cloud Functions allows you to write your code without worrying about provisioning resources or scaling to handle changing requirements.
There are two types of Cloud Functions:
- HTTP functions respond to HTTP requests. You'll build one in this codelab.
- Background functions are triggered by events, like a message being published to Cloud Pub/Sub or a file being uploaded to Cloud Storage. We don't address this in this lab, but you can read more in the documentation.
This codelab will walk you through creating your own Google Cloud Function in Go.
What you will build
In this codelab, you will publish and Cloud Function that when invoked via HTTP will display an image of the Go gopher, designed by Renee French.
What you will learn
How to write an HTTP Cloud Function in Go.
How to test an HTTP Cloud Function in Go.
How to run a local Go HTTP server to try the function.
What you will need
A text editor, like the editor built into Cloud Shell
Before you click the Start Lab button
Read these instructions. Labs are timed and you cannot pause them. The timer, which starts when you click Start Lab, shows how long Google Cloud resources will be made available to you.
This hands-on lab lets you do the lab activities yourself in a real cloud environment, not in a simulation or demo environment. It does so by giving you new, temporary credentials that you use to sign in and access Google Cloud for the duration of the lab.
To complete this lab, you need:
- Access to a standard internet browser (Chrome browser recommended).
- Time to complete the lab---remember, once you start, you cannot pause a lab.
How to start your lab and sign in to the Google Cloud Console
Click the Start Lab button. If you need to pay for the lab, a pop-up opens for you to select your payment method. On the left is the Lab Details panel with the following:
- The Open Google Console button
- Time remaining
- The temporary credentials that you must use for this lab
- Other information, if needed, to step through this lab
Click Open Google Console. The lab spins up resources, and then opens another tab that shows the Sign in page.
Tip: Arrange the tabs in separate windows, side-by-side.
Note: If you see the Choose an account dialog, click Use Another Account.
If necessary, copy the Username from the Lab Details panel and paste it into the Sign in dialog. Click Next.
Copy the Password from the Lab Details panel and paste it into the Welcome dialog. Click Next.
Important: You must use the credentials from the left panel. Do not use your Google Cloud Skills Boost credentials. Note: Using your own Google Cloud account for this lab may incur extra charges.
Click through the subsequent pages:
- Accept the terms and conditions.
- Do not add recovery options or two-factor authentication (because this is a temporary account).
- Do not sign up for free trials.
After a few moments, the Cloud Console opens in this tab.
Activate Cloud Shell
Cloud Shell is a virtual machine that is loaded with development tools. It offers a persistent 5GB home directory and runs on the Google Cloud. Cloud Shell provides command-line access to your Google Cloud resources.
Click Activate Cloud Shell at the top of the Google Cloud console.
It takes a few moments to provision and connect to the environment. When you are connected, you are already authenticated, and the project is set to your PROJECT_ID. The output contains a line that declares the PROJECT_ID for this session:
gcloud is the command-line tool for Google Cloud. It comes pre-installed on Cloud Shell and supports tab-completion.
(Optional) You can list the active account name with this command:
(Optional) You can list the project ID with this command:
gcloud, in Google Cloud, refer to the gcloud CLI overview guide.
Ensure the Cloud Functions API is enabled
Run the following command from Cloud Shell to make sure the Cloud Functions API is enabled. This will make sure we can deploy Cloud Functions later in the codelab.
Download and setup the code
From the Cloud Shell terminal, use
curl to download a zip with the code for this lab:
unzip to unpack the code. This unpacks a directory (
golang-samples-main), which contains sample Go code for cloud.google.com:
Change to the directory containing the code for this codelab:
gopher directory contains the following directories and files:
Introducing HTTP Cloud Functions in Go
HTTP Cloud Functions in Go are written as http.HandlerFunc functions, which is an interface defined in the Go standard library. The function must:
- Be exported, meaning it can be used from another package, which is indicated by the name starting with an uppercase letter.
- Match the
http.HandlerFunctype, meaning the function is of the form
func(http.ResponseWriter, *http.Request). (See the Writing Web Applications tutorial for an in-depth guide to writing a full web application in Go.)
For example, here is a "Hello, world" function:
Deploy this function as an HTTP Cloud Function!
functions/codelabs/gopher directory you can deploy the function name with
gcloud functions deploy:
This will take a minute or two.
Click Check my progress to verify the objective.
Did you get an error during deployment? Check:
- Is the Cloud Functions API enabled? If not, there will be an error with a link allowing you to enable it. Otherwise, you can enable it with the command
gcloud services enable cloudfunctions.googleapis.com.
- Be sure your working directory (where you're running
gcloudfrom) is the directory with the
.gofile in it. You can change directories using
- Is the function name correct? It should be
HelloWorld, the name of the Go function we're trying to deploy.
httpsTrigger URL that's displayed in the output. It will have a form like this:
To test the
curl into the URL from the last output:
You've written and deployed a HTTP Cloud Function!
Writing the Gopher HTTP Cloud Function
Now make the "Hello, world" function a bit more entertaining by printing an image of a Gopher for every request.
The following block shows the code to make it happen. You can see this code in Cloud Shell at
- The file starts with a package declaration and comment. All Go code is written inside a package, with a declaration like this at the top.
importblock contains a list of other packages that this file depends on. These packages are referred to in the rest of the file using their name. For example, to use the
ResponseWritertype from the
httppackage, you write
- Next is the
- The function starts by reading the
gophercolor.pngfile (see the sample code) using the
- Then, it checks whether there was an error reading the file, which might occur if the file is corrupted or was accidentally left out of the upload.
- It uses
io.Copyto copy the gopher image to
http.ResponseWriterargument. Everything written to
wwill be sent in the HTTP response.
- If there was no error when writing the response, the function returns normally.
Deploy this function as you did the "Hello, world" function from before, using
gcloud functions deploy and the name of the function,
To test the function, visit the function's URL in the output from the last command. If everything is working correctly, you will see the gopher in your browser!
The next step is to add a test to make sure your function continues to work.
Click Check my progress to verify the objective.
Writing a test
HTTP Cloud Functions in Go are tested using the testing and httptest packages from the standard library. There is no need to run an emulator or other simulation to test your function—just normal Go code.
Here is what a test looks like for the
- Go tests are written the same way as other Go files. They start with a package declaration and set of imports.
- The test declaration is of the form
func MyTest(t *testing.T). It must be exported and take one argument of type
- The test creates test response and request values using the
- It calls the Gopher function.
- After invoking the Gopher function, the test checks the HTTP response code to be sure there were no errors.
To run these tests locally,
cd to the directory with the files you're testing: ???
golang-samples-main/functions/codelabs/gopher directory, use the
go test command:
Test not passing?
- Check the error message for anything helpful.
- Are you in the same directory as the
Next, you'll create a binary (
package main, in Go) so that you can run your function locally and try it in a browser.
Running the function locally
To run an HTTP function locally, create an HTTP server and register your function as a handler. (See the Writing Web Applications tutorial for an in-depth guide to writing a full web application in Go.)
You can write an HTTP server for your function in a subdirectory of your function.
Following a Go convention, you name that directory
cmd and create a
main.go file inside it:
- This file uses
package mainas the package. A
mainpackage will be built as a binary that you can run.
- This file imports
github.com/GoogleCloudPlatform/golang-samples/functions/codelabs/gopher, based on the
moduleline of the
go.modnext to your function file. When you're writing your own functions, you can name the module whatever you prefer.
func main()is the entry point for the binary. It registers the
gopher.Gopherfunction as an HTTP handler then starts the server using
To build and run this binary locally, run the following commands:
Because the function loads the
gophercolor.png image from the current working directory, you have to start your binary from the same directory as the
gophercolor.png file. The
-o start flag says to name the output binary
./cmd says to build the binary located in the
Now use the Cloud Shell Web Preview to test the server in your browser. Click the Web Preview button and then select port
8080 from the displayed menu.
Cloud Shell opens the preview URL on its proxy service in a new browser window. The web preview restricts access over HTTPS to your user account only.
If everything is working properly, you should see the Go Gopher!
Can't see the gopher?
- Are you in the same directory as the
- Is the server started? Be sure to build it with the
go build -o start ./cmdcommand, then start it by running
./start. It should print
Listening on localhost:8080.
- Did you select the right port when opening the web preview? Be sure to use
8080, the port the server is listening on.
For this lab, Qwiklabs will delete all resources you've used. It's always a good idea to know what you would need to do on your own environment to save on cost and to be a good cloud citizen.
Stop serving your URL with Ctrl + c
Once you're done testing your Cloud Functions, you can delete it using
You can also delete the function from the Cloud Console.
We hope you enjoy using Cloud Functions in Go!
Finish Your Quest
This self-paced lab is part of the Qwiklabs Getting Started with Go on Google Cloud Quest. A Quest is a series of related labs that form a learning path. Completing this Quest earns you the badge above, to recognize your achievement. You can make your badge (or badges) public and link to them in your online resume or social media account. Enroll in this Quest and get immediate completion credit if you've taken this lab. See other available Qwiklabs Quests.
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Manual Last Updated June 3, 2022
Lab Last Tested June 3, 2022
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