Golang is an increasingly popular programming language, and its application areas on the server side are increasing day by day. Developers all know that network requests are an essential part of server-side development, so how to perform network requests in Golang? This article will explain the Golang request package in detail so that everyone can better understand the use of Golang network requests.

What is a request package?

The request package is a toolkit used in the Golang standard library to make network requests. It provides multiple request methods such as http, net, websocket, etc., as well as basic request methods, request headers, request bodies and other functions. When sending an http request, we need to assemble the request header and request body, specify the request method, request address and port number, and then make a request to the server. The request package explains how to perform these operations, which greatly facilitates our network development.

HTTP request

In Golang, to send HTTP requests, you need to use the Client and Request structures provided by the net/http library. The Client structure represents an HTTP client, and the Request structure represents an HTTP request. We use Client to send Request requests. Here's how to send a GET request:

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

func main() {
    resp, err := http.Get("http://example.com/")
    if err != nil {
        // handle error
    }
    defer resp.Body.Close()
    body, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        // handle error
    }
    fmt.Println(string(body))
}

This code will send a GET request to the http://example.com/ address, and then print the response information returned by the server. We use the http.Get method to send the request and return error information if an error occurs. Remember to close the response body after the request is completed to avoid unnecessary waste of resources.

In addition to GET requests, we can also send POST, PUT, DELETE and other request methods. We only need to use the Client's Do method and pass in the Request request. The following is an example of a POST request:

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

func main() {
    url := "http://example.com/api"
    jsonData := []byte(`{"key":"value"}`)

    req, err := http.NewRequest("POST", url, bytes.NewBuffer(jsonData))
    req.Header.Set("Content-Type", "application/json")
    
    client := &http.Client{}
    resp, err := client.Do(req)
    if err != nil {
        // handle error
    }
    defer resp.Body.Close()
    
    // handle response
}

In the POST request, we need to specify the request method as POST and pass in the request address and request body. There is something to note here. POST requests need to set the Content-Type field in the request header to inform the server of the data type of the request body. Here, we use the json package in golang to convert the request body into json format and pass it into the request body.

WebSocket request

WebSocket is a protocol provided in HTML5 for full-duplex communication between the browser and the server. In Golang, we can use the Dial method provided by the websocket library to establish a WebSocket connection, and use the WriteMessage and ReadMessage methods for data exchange. The following is an example of a WebSocket connection:

import (
    "fmt"
    "log"
    "net/url"
    "github.com/gorilla/websocket"
)

func main() {
    u := url.URL{Scheme: "ws", Host: "echo.websocket.org", Path: "/"}
    fmt.Println("connecting to ", u.String())

    conn, _, err := websocket.DefaultDialer.Dial(u.String(), nil)
    if err != nil {
        log.Fatal("dial:", err)
    }
    defer conn.Close()

    message := []byte("hello, world!")
    err = conn.WriteMessage(websocket.TextMessage, message)
    if err != nil {
        log.Println("write:", err)
        return
    }

    _, p, err := conn.ReadMessage()
    if err != nil {
        log.Println("read:", err)
        return
    }
    fmt.Printf("received: %s\n", p)
}

This code will establish a WebSocket connection to https://echo.websocket.org, then send a "hello, world!" text message, and print the service The response message returned by the client. We used the Dial method provided by the websocket library to establish a connection, and used the WriteMessage method to send messages and the ReadMessage method to receive messages. Compared with HTTP requests, WebSocket requests have higher real-time and real-time performance.

Summary

This article explains in detail the request package in Golang, including HTTP requests, WebSocket requests, and request assembly and sending. By studying this article, we can better master the usage and techniques of Golang network requests, and provide more tools and methods for server-side development.

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