# Hello Gin

> Simple basics on a GET and POST request for Gin in Go.

- Canonical: https://dennisokeeffe.com/blog/2018-12-25-hello-gin
- Published: 2018-12-25
- Updated: 2018-12-25

A simple implementation of the Gin web framework for go.

## Installation

```shell
go get -u github.com/gin-gonic/gin
```

## Hello world

```go
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(":3000") // listen and serve on 0.0.0.0:8080
}
```

If we now run `go run main.go` we can start the server on port 3000. Either using `curl http://localhost:3000` or a GUI like Postman, we can see the results:

![GET ping](https://res.cloudinary.com/gitgoodclub/image/upload/v1538628243/getCLI-compressed.png "GET ping")
![GET postman](https://res.cloudinary.com/gitgoodclub/image/upload/v1538628243/getPostman-compressed.png "GET Postman")

## Handling JSON data

We need to bind the JSON data to a struct. Let's update the code to have the following:

```go
package main

// Update here
import "github.com/gin-gonic/gin"
import "net/http"
import "fmt"

// Update here
type PostData struct {
    Hello string `json:"hello"`
}

func main() {
    r := gin.Default()
    r.GET("/ping", func(c *gin.Context) {
        c.JSON(200, gin.H{
            "message": "pong",
        })
    })

    // Update here
    r.POST("/post", func(c *gin.Context) {
        var json PostData
        c.BindJSON(&json)
        id := c.Query("id") // shortcut for c.Request.URL.Query().Get("id")
        page := c.DefaultQuery("page", "0")
        hello := json.Hello
        res := fmt.Sprintf("id: %s; page: %s; hello: %s", id, page, hello)
        fmt.Printf(res)

        c.String(http.StatusOK, res)
    })

    r.Run(":3000")
}
```

First, we update the imports to include the `fmt` and `net/http` libraries:

```go
import "github.com/gin-gonic/gin"
import "net/http"
import "fmt"
```

Secondly, we create a struct that can have the JSON data bound to it:

```go
type PostData struct {
    Hello string `json:"hello"`
}
```

Finally, we add a `POST` route that, for the sake of the example, takes two queries ("page" has a default value) and binds the JSON data to the struct.

```go
r.POST("/post", func(c *gin.Context) {
    var json PostData
    c.BindJSON(&json)
    id := c.Query("id") // shortcut for c.Request.URL.Query().Get("id")
    page := c.DefaultQuery("page", "0")
    hello := json.Hello
    res := fmt.Sprintf("id: %s; page: %s; hello: %s", id, page, hello)
    fmt.Printf(res)

    c.String(http.StatusOK, res)
})
```

Finally, we log the result out and send back the `res` string to Postman.

Results:

![POST post](https://res.cloudinary.com/gitgoodclub/image/upload/v1538628243/postCLI-compressed.png "POST post")
![POST postman](https://res.cloudinary.com/gitgoodclub/image/upload/v1538628244/postPostman-compressed.png "POST Postman")

For more information and documentation, check out [Gin's github](https://github.com/gin-gonic/gin).

For my repo, [check here](https://github.com/okeeffed/hello-gin)

_**Hello** is a series that is about short, sharp examples. Read more on this series to find small gems to add your toolset._