GO pretty print

info

Here are some examples on how you may want to pretty print json or an http response.

JSON

Before Pretty Printing

Given the following struct:

type Person struct {
	Name   string `json:"name"`
	Age    int    `json:"age"`
	Email  string `json:"email"`
	Active bool   `json:"active"`
}

p := Person{
	Name:   "John Doe",
	Age:    30,
	Email:  "[email protected]",
	Active: true,
}

If you use the json.Marshal method:

jsonData, err := json.Marshal(p)
if err != nil {
	log.Fatal(err)
}
fmt.Println(string(jsonData))

The output will be:

{"name":"John Doe","age":30,"email":"[email protected]","active":true}

After Pretty Printing

jsonData, err := json.MarshalIndent(p, "", "    ")
if err != nil {
	log.Fatal(err)
}
fmt.Println(string(jsonData))

The output will be:

{
    "name": "John Doe",
    "age": 30,
    "email": "[email protected]",
    "active": true
}

HTTP Request

Before Pretty Printing

If you were to use the standard json.Marshal method:

jsonData, err := json.Marshal(info)
if err != nil {
	log.Fatal(err)
}
fmt.Println(string(jsonData))

Given a request to http://localhost:8080/example?query=test with the header User-Agent: MyBrowser and method GET, the output might look something like:

{"method":"GET","url":"/example?query=test","headers":{"User-Agent":["MyBrowser"]},"host":"localhost:8080","remoteAddr":"[::1]:12345","requestURI":"/example?query=test"}

This is a compact representation that's not very human-readable.

After Pretty Printing

Using the printRequestInfo function which employs json.MarshalIndent:

printRequestInfo(r)

The output will be:

{
    "method": "GET",
    "url": "/example?query=test",
    "headers": {
        "User-Agent": ["MyBrowser"]
    },
    "host": "localhost:8080",
    "remoteAddr": "[::1]:12345",
    "requestURI": "/example?query=test"
}

Here's the custom printRequestInfo function:

type RequestInfo struct {
	Method    string      `json:"method"`
	URL       string      `json:"url"`
	Header    http.Header `json:"headers"`
	Host      string      `json:"host"`
	RemoteAddr string     `json:"remoteAddr"`
	RequestURI string     `json:"requestURI"`
}

func printRequestInfo(r *http.Request) {
	info := RequestInfo{
		Method:    r.Method,
		URL:       r.URL.String(),
		Header:    r.Header,
		Host:      r.Host,
		RemoteAddr: r.RemoteAddr,
		RequestURI: r.RequestURI,
	}

	jsonData, err := json.MarshalIndent(info, "", "    ")
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(string(jsonData))
}