golang http asynchronous request

In many modern web applications, asynchronous processing is one of the most important features. In Go language, it provides a simple but powerful way to complete asynchronous requests - using the http package. This article will introduce how to use golang's http package to make asynchronous requests.

1. Introduction

The http package in Go language is a very powerful package that can be used to send GET, POST and other various HTTP requests. It also provides a client to interact with the HTTP server. In the basic case, the http package provides a very simple way to send synchronous requests, but we usually need an asynchronous solution. Fortunately, the http package provides some simple yet powerful functionality for handling asynchronous requests. "In Go, we implement asynchronous requests through goroutine, which allows Go to easily handle a large number of highly concurrent asynchronous requests.

2. Usage method

1. Create a client

In Go, the client object in the http package can be used to perform asynchronous HTTP requests. We can create a default client through the following code:

package main

import (
    "net/http"
)

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

In the above example, we A default HTTP client object is created and assigned to the variable "client".

2. Send a request

After creating the HTTP client, we can use the http.NewRequest function Create an HTTP request object. HttpClient performs the request and receives the response by calling Do. To make the request asynchronous, we need to use a goroutine. Here is the sample code:

package main

import (
    "fmt"
    "net/http"
)

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

    req, err := http.NewRequest("GET", "https://www.google.com", nil)
    if err != nil {
        fmt.Println(err)
        return
    }

    go func() {
        resp, err := client.Do(req)
        if err != nil {
            fmt.Println(err)
            return
        }
        defer resp.Body.Close()
        fmt.Println("Async response status:", resp.Status)
    }()

    fmt.Println("Request sent asynchronously.")
    //等待goroutine结束
    //time.Sleep(5 * time.Second)
}

In the above code, we first create An HTTP client and then created a GET request object using the http.NewRequest() function. We then used a goroutine to build an asynchronous request. The code that sends the request is outside the goroutine and outputs "Request sent asynchronously.". The rest of the code Output the status of the asynchronous request. Please note that we called resp.Body.Close() in the defer statement to close the response body.

3. Error handling

When we send an asynchronous HTTP request When the server responds too slowly or due to network problems, the client may Timeout waiting for a response. In order to solve this problem, we can control the timeout and cancellation of the request through the SetTimeout and CancelRequest functions. The following is the sample code:

package main

import (
    "context"
    "fmt"
    "net/http"
    "time"
)

func main() {
    client := &http.Client{
        Timeout: 5 * time.Second,
    }

    req, err := http.NewRequest("GET", "https://www.google.com", nil)
    if err != nil {
        fmt.Println(err)
        return
    }

    ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
    defer cancel()

    req = req.WithContext(ctx)

    go func() {
        resp, err := client.Do(req)
        if err != nil {
            fmt.Println(err)
            return
        }
        defer resp.Body.Close()
        fmt.Println("Async response status:", resp.Status)
    }()

    fmt.Println("Request sent asynchronously.")
}

In the above example, we first set the timeout of the client for 5 seconds. Then, a new context and request object are created using the WithTimeout function in the context package. This function will return a cancellation function, which we call using a defer statement to ensure that the request thread is canceled before the function completes ( If it still exists).

2. Network Connection Error

An error that often occurs is the network connection error. This is usually related to devices with slow network speeds. To solve network connection problems, we The connection timeout can be set using the Dialer function provided in http.Transport. The following is the sample code:

package main

import (
    "context"
    "fmt"
    "net"
    "net/http"
    "time"
)

func main() {
    dialer := &net.Dialer{
        Timeout: 5 * time.Second,
    }

    transport := &http.Transport{
        DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
            return dialer.DialContext(ctx, network, addr)
        },
    }

    client := &http.Client{
        Transport: transport,
    }

    req, err := http.NewRequest("GET", "https://www.google.com", nil)
    if err != nil {
        fmt.Println(err)
        return
    }

    go func() {
        resp, err := client.Do(req)
        if err != nil {
            fmt.Println(err)
            return
        }
        defer resp.Body.Close()
        fmt.Println("Async response status:", resp.Status)
    }()

    fmt.Println("Request sent asynchronously.")
}

Using the above method again, we set the dialer's timeout to 5 seconds. Then, the client uses http The DialContext function provided in .Transport makes the request. This function will use the Dialer we set for the network connection and close the connection after timeout. Note that we need to make sure we close the response body after receiving the response.

4. Conclusion

In this article, we introduced the method of using the http package to perform asynchronous HTTP requests in the Go language. We created goroutine to send requests asynchronously and introduced common error handling methods. This approach is very simple but powerful and can handle high concurrency situations that may arise in web applications, making it more flexible than most traditional network libraries. Now you can apply this technique to your code, saving valuable time and resources.

The above is the detailed content of golang http asynchronous request. For more information, please follow other related articles on the PHP Chinese website!