Deploy a RESTful Go API with Gin on Koyeb

In this guide, we will explain how to build and deploy a Go API using the Gin framework on the Koyeb serverless platform.

Gin is a web framework written in Go focusing on performance. It provides an elegant way to write web applications and microservices and comes with a set of commonly used primitives like routing, middleware, rendering, and more.

By deploying your application on Koyeb, you benefit from powerful primitives including native autoscaling, automatic HTTPS (SSL), auto-healing, and global load-balancing across our edge network with zero configuration.

Requirements

To successfully follow and complete this guide, you need:

• The Go programming language installed
• Docker installed on your machine
• A Koyeb account to deploy and run the Go web API
• The Koyeb CLI installed to interact with Koyeb from the command line
• Have a registry that we will use to store our Go web app Docker image and deploy it on Koyeb

Steps

To successfully complete this guide and deploy the Go API on Koyeb, you need to follow these steps:

1. Building the Go API using Gin
2. Dockerize the Go application
3. Deploy the Dockerized Go API on Koyeb

Building the Go API using Gin

First, let's get started by creating a new directory in your GOPATH to build our sample application:

mkdir $GOPATH/src/go-demo
cd $GOPATH/src/go-demo

In this guide, we name the directory go-demo. You can name the folder whatever you like.

Next, run go mod init to create a go.mod file and track your code's dependencies. As you add dependencies, the go.mod file will list the versions your code depends on allowing you to keep your builds reproducible and gives you direct control over which module versions to use.

In your project folder, create a new file named server.go with the following content inside:

package main

import (
    "fmt"
    "os"

    "github.com/gin-gonic/gin"
)

func main() {
    port := os.Getenv("PORT")

    if port == "" {
        port = "8000"
    }

    r := gin.Default()

    r.GET("/", func(c *gin.Context) {
        c.JSON(200, gin.H{
            "message": "Hello, world!",
        })
    })

    r.GET("/:name", func(c *gin.Context) {
        name := c.Param("name")

        c.JSON(200, gin.H{
            "message": fmt.Sprintf("Hello, %s!", name),
        })
    })

    r.Run(fmt.Sprintf(":%s", port))
}

The code above launch a Gin server listening on port 8000 by default with two API routes configured:

• / returning "Hello, world!"
• /:name returning "Hello, :name!" where :name is the string passed in parameter, i.e /john will return "Hello, john!".

Then, in your terminal execute go mod tidy to add missing modules required by our project and add github.com/gin-gonic/gin as a project dependency.

You can now run the application locally running go run server.go and navigate in your browser at http://localhost:8000.

Dockerize the Go application

To Dockerize our Go application, create a Dockerfile in your project directory.
In this guide, we use Docker multi-stage build to keep the image layers size as small as possible and to ensure our image contains only what is needed to run.

In your Dockerfile, copy the content below:

FROM golang:1.16-alpine AS builder
WORKDIR /app
COPY . .
RUN go mod download
RUN go build -o ./go-demo ./server.go


FROM alpine:latest AS runner
WORKDIR /app
COPY --from=builder /app/go-demo .
EXPOSE 8000
ENTRYPOINT ["./go-demo"]

The first stage is used to install dependencies and build our application, in the second one we copy the application binary from stage one and use it to run the application.

To build the Docker image execute the following command in your terminal:

docker build . -t <DOCKER_HUB_USERNAME>/go-demo

In this guide we will push the Docker image to the Docker Hub. You are free to use another different registry as Koyeb allows you to deploy from any container registry.

Once the build is completed, you can run a container using the image locally to validate everything is working as expected running:

docker run -p 8000:8000 <DOCKER_HUB_USERNAME>/go-demo

If everything goes well, your container starts properly, you can test the routes using curl:

$curl localhost:8000/
Hello, world!

Next, we can push the Docker image to a container registry, in this guide, the Docker Hub using the following command:

docker push <DOCKER_HUB_USERNAME>/go-demo

On the push command is completed, the Docker image is stored on the container registry and we can deploy it on Koyeb.

Deploy the Dockerized Go API on Koyeb

We are now ready to deploy our Go web application on Koyeb. First, create a Koyeb Secret to store your container registry configuration.
In this guide, we will deploy our app from the Docker Hub. For other container registries example, check out the related documentation.

Note: if your Docker image is public, there is no need to create a secret containing your container registry configuration.

echo \
'{
  "auths": {
    "index.docker.io/v1/": {
      "username": "<REPLACE_ME_WITH_DOCKER_HUB_USERNAME>",
      "password": "<REPLACE_ME_WITH_DOCKER_HUB_TOKEN>"
    }
  }
}' | koyeb secrets create docker-hub-credentials --value-from-stdin

We can now deploy the Go web application on Koyeb Serverless Platform running:

koyeb app init go-demo --docker "<REPLACE_ME_WITH_DOCKER_HUB_USERNAME>/go-demo" --ports 8000:http --routes /:8000 --docker-private-registry-secret docker-hub-credentials

This command creates a new Koyeb App and deploys our Go application exposing port 8000 and making it publicly accessible on the / route of your Koyeb App URL.

To retrieve your Koyeb App URL and access your application, run:

$koyeb app get go-demo
ID                                      NAME            DOMAINS                                 UPDATED AT
d58ebed1-48c0-46b7-a2f1-91f3ffdbccf2    go-demo         go-demo-<YOUR_ORG>.koyeb.app    2021-06-23 09:46:55.411403 +0000 UTC

Open the URL in your browser to access your application running on Koyeb and natively offering autoscaling, automatic HTTPS (SSL), auto-healing, and global load-balancing across our edge network.