golang close httpclient

In the Go language, http Client is a very commonly used network request library. During network requests, in order to optimize performance and release resources, we often need to close the http Client in time after the request is completed. So, how to close http Client in Go language? This article will introduce how to close http Client and some precautions.

Method to close Http Client

In Go language, closing http Client is achieved by calling the Close method of http Client. The Close method of http Client will release all connections, including unclosed connections. Generally speaking, we should call the http Client's Close method promptly after the request is completed to release resources.

The sample code is as follows:

package main

import (
    "fmt"
    "net/http"
)

func main() {
    client := http.Client{}
    req, _ := http.NewRequest("GET", "http://www.example.com", nil)

    resp, err := client.Do(req)
    if err != nil {
        fmt.Println("Error:", err)
    }

    defer resp.Body.Close()
    defer client.Close()

    fmt.Println(resp.Body)
}

In the above sample code, we use http Client to send a GET request, and call the Close method of http Client after the request is completed.

Notes

When using http Client, we need to pay attention to the following points:

1. Reuse http Client: In some cases, we need to reuse http Client, this can avoid creating a new http Client for each request. We can pass in a reused http.Client when calling the Do method.

package main

import (
    "fmt"
    "net/http"
)

func main() {
    transport := http.DefaultTransport.(*http.Transport).Clone()
    client := http.Client{Transport: transport}

    req1, _ := http.NewRequest("GET", "http://www.example.com", nil)
    resp1, err := client.Do(req1)
    if err != nil {
        fmt.Println("Error:", err)
    }

    req2, _ := http.NewRequest("GET", "http://www.example.com", nil)
    resp2, err := client.Do(req2)
    if err != nil {
        fmt.Println("Error:", err)
    }

    defer resp1.Body.Close()
    defer resp2.Body.Close()

    fmt.Println(resp1.Body)
    fmt.Println(resp2.Body)
}

In the above sample code, we first copied the http.DefaultTransport and then created a new http Client. Then we sent two GET requests respectively and read the Body from the response respectively.

2. Concurrent requests: When making concurrent requests, we also need to pay attention to the use of http Client. If multiple requests are sent at the same time, it is unwise to create a new http Client for each request. This will lead to a waste of system resources and possible deadlocks. Therefore, we should reuse the existing http Client.

package main

import (
    "fmt"
    "net/http"
)

func main() {
    client := &http.Client{}

    respChan := make(chan *http.Response)

    get := func(url string) {
        req, _ := http.NewRequest("GET", url, nil)
        resp, _ := client.Do(req)
        defer resp.Body.Close()

        respChan <- resp
    }

    urls := []string{"http://www.example.com", "http://www.example.org", "http://www.example.net"}
    for _, url := range urls {
        go get(url)
    }

    for range urls {
        resp := <-respChan
        fmt.Println(resp.Body)
    }

    client.Close()
}

In the above sample code, we sent three GET requests concurrently. We use a respChan channel to receive the response for each request. In the loop, we read each response from the respChan channel and output the response's Body.

Conclusion

It is very important to close the http Client. If it is not closed in time, it will cause a waste of system resources and may even cause serious problems. When using http Client, we need to pay attention to some issues such as concurrent requests and reusing http Client to optimize performance and release resources. In Go language, to close the http Client, you only need to call the Close method.

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