How to use the standard library to initiate HTTP requests in Go language

Go language (Golang) is an efficient programming language developed by Google, especially suitable for network programming and system programming. In web applications, sending HTTP requests is a very common operation. This article will introduce how to use the standard library to initiate HTTP requests in the Go language.

1. Basic structure of HTTP request

Before initiating an HTTP request, you must first understand the various parts of the HTTP request.

HTTP request consists of three parts: request line, request header and request body.

The request line contains the requested method, URL and protocol version, for example:

GET /api/users HTTP/1.1

The request header contains the metadata of the HTTP request, for example:

User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.8

The request body contains the application The data to be submitted, for example:

{"username":"admin","password":"123456"}

2. Use the standard library to initiate an HTTP GET request

The following is an example of using the standard library to initiate an HTTP GET request Example:

package main

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

func main() {
    resp, err := http.Get("https://www.example.com")
    if err != nil {
        panic(err)
    }
    defer resp.Body.Close()

    body, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        panic(err)
    }

    fmt.Println(string(body))
}

In the above example, we initiated an HTTP GET request using the http.Get function. This function returns a http.Response type structure, which contains various parts of the HTTP response. We use the ioutil.ReadAll function to read the contents of the response body and output it to the console.

3. Use the standard library to initiate an HTTP POST request

In addition to the HTTP GET request, we can also use the standard library to initiate an HTTP POST request. Here is an example of making an HTTP POST request using the standard library:

package main

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

func main() {
    url := "http://www.example.com/api/login"
    data := []byte(`{"username":"admin","password":"123456"}`)
    req, err := http.NewRequest("POST", url, bytes.NewBuffer(data))
    if err != nil {
        panic(err)
    }
    req.Header.Set("Content-Type", "application/json")

    client := &http.Client{}
    resp, err := client.Do(req)
    if err != nil {
        panic(err)
    }
    defer resp.Body.Close()

    body, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        panic(err)
    }

    fmt.Println(string(body))
}

In the above example, we created an HTTP request using the http.NewRequest function. We specified the request method as POST, the URL as http://www.example.com/api/login, and set the request body as {"username":"admin"," password":"123456"}. We also set the Content-Type of the request header to application/json. Finally, we use the client.Do method to perform an HTTP POST request and read the contents of the response body.

4. Use third-party libraries to initiate HTTP requests

In addition to the standard library, we can also use third-party libraries to initiate HTTP requests. Here is an example of making an HTTP GET request using the third-party library github.com/go-resty/resty:

package main

import (
    "fmt"
    "github.com/go-resty/resty/v2"
)

func main() {
    client := resty.New()

    resp, err := client.R().
        EnableTrace().
        Get("https://www.example.com")
    if err != nil {
        panic(err)
    }

    fmt.Println(string(resp.Body()))
}

In the above example, we used github. The Get method provided by the com/go-resty/resty library initiates an HTTP GET request. We also used the EnableTrace method to print the details of the HTTP request.

5. Conclusion

Through the introduction of this article, we have learned how to use the standard library or third-party library to initiate HTTP requests in the Go language. Understanding the basic structure and usage of HTTP requests is very important for developing web applications. In actual development, we also need to consider issues such as the security and performance of HTTP requests.

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