# Build Golang API using Gin and Docker

### Build Golang API

Gin is a popular golang framewrok (https://github.com/gin-gonic/gin).

This code (main.go) is to build a basic GET verb API to test.

package main

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

func main() {
    r := gin.Default()
    r.GET("/ping", func(c *gin.Context) {
        c.JSON(200, gin.H{
            "message": "pong",
        })
    })
    r.Run() // listen and serve on 0.0.0.0:8080 (for windows "localhost:8080")
}

We gonna create Go module to manage its dependencies.

$ go mod init henry-on-the-internet.com/main
$ go mod tidy

We can start the API service.

` $ go run main.go`

We can test it via Postman, visiting it on browsers or curl.

http://localhost:8080/ping

---

### Containerize your API vid Docker commands

Install Docker an run it

> `--rm` tells docker to remove this image after executing it.
> `-v` tells docker where to store the program
> `-w` tells docker where is working directory
> `-p` tells docker how to publish the port mapping

We can test it using the same methods.


---

### Create an automated build using Dockerfile

Create a file called Dockerfile in the folder main.go is inside

From golang:1.18

WORKDIR /go/src/app

COPY . .

RUN go build -o main main.go

CMD ["./main"]

Build and run it via commands

$ docker build -t myapp .
$ docker run --rm -p 8080:8080 myapp

Note: Remember do not configure our API to listen the port only on localhost `r.Run(localhost:8080)`

It is not reachable when we dockerizer it. We can find the IP address using the following command. 

$ docker ps
0.0.0.0:8080->8080/tcp, :::8080->8080/tcp