Go tutorial: 2. Create an HTTP request and server

This article was originally published on GitHub.

nat/http package

Create a request

$ touch request.go

// request.go
package main

import (
    "fmt"
    "io/ioutil"
    "net/http"
)

func main() {
    res, err := http.Get("https://api.github.com/users/defunkt")
    if err != nil {
        panic(err)
    }
    defer res.Body.Close()

    body, err := ioutil.ReadAll(res.Body)

    fmt.Println(string(body))
}

$ go run request.go | jq
{
  "login": "defunkt",
  "id": 2,
  "node_id": "MDQ6VXNlcjI=",
  "avatar_url": "https://avatars0.githubusercontent.com/u/2?v=4",
  "gravatar_id": "",
  "url": "https://api.github.com/users/defunkt",
  "html_url": "https://github.com/defunkt",
  "followers_url": "https://api.github.com/users/defunkt/followers",
  "following_url": "https://api.github.com/users/defunkt/following{/other_user}",
  "gists_url": "https://api.github.com/users/defunkt/gists{/gist_id}",
  "starred_url": "https://api.github.com/users/defunkt/starred{/owner}{/repo}",
  "subscriptions_url": "https://api.github.com/users/defunkt/subscriptions",
  "organizations_url": "https://api.github.com/users/defunkt/orgs",
  "repos_url": "https://api.github.com/users/defunkt/repos",
  "events_url": "https://api.github.com/users/defunkt/events{/privacy}",
  "received_events_url": "https://api.github.com/users/defunkt/received_events",
  "type": "User",
  "site_admin": true,
  "name": "Chris Wanstrath",
  "company": "@github ",
  "blog": "http://chriswanstrath.com/",
  "location": "San Francisco",
  "email": null,
  "hireable": true,
  "bio": "🍔 ",
  "public_repos": 107,
  "public_gists": 273,
  "followers": 20213,
  "following": 210,
  "created_at": "2007-10-20T05:24:19Z",
  "updated_at": "2018-06-05T19:29:51Z"
}

Setup a server

$ touch server.go

// server.go
package main

import (
    "fmt"
    "log"
    "net/http"
)

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        fmt.Fprintf(w, "Hello, %q", r.URL.Path)
    })

    fmt.Println("http://localhost:8080")
    log.Fatal(http.ListenAndServe(":8080", nil))
}

$ go run server.go
http://localhost:8080
...

$ curl http://localhost:8080
Hello, "/"

json package

$ touch json.go

// json.go
package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    str := []byte(`{"id":1,"name":"Gopher"}`)
    data := struct {
        ID   int    `json:"id"`
        Name string `json:"name"`
    }{}

    if err := json.Unmarshal(str, &data); err != nil {
        panic(data)
    }
    fmt.Println("ID: ", data.ID, "Name: ", data.Name)
}

$ go run json.go
ID:  1 Name:  Gopher

Exercise 2-1

Create an application request.go which creates a GET request to https://api.github.com/users/defunkt and parses the response body with json.Unmarshal only login, id, site_admin, and bio.

$ go run request.go
Login:  defunkt
ID:  2
SiteAdmin:  true
Bio:  🍔

The answer is request.go

Exercise 2-2

Create an application server.go which builds a server. It has three endpoints, /, /json, and /404. / returns Hello, "/". /json returns {"id":1,"name":"my_name","mail_address":""}. /404 returns Not Found, /404 with the 404 status code.

$ go run server.go
http://localhost:8080

$ curl http://localhost:8080/
Hello, "/"

$ curl http://localhost:8080/json
{"id":1,"name":"my_name","mail_address":""}

$ curl http://localhost:8080/404
Not Found, /404

The answer is server.go.

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