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Advanced Techniques in Go Programming

Setting the Timeout Period on the Client Side

Explore how to set timeout periods on the client side in Go web services. Understand how to use context.WithTimeout and cancellation to manage slow HTTP requests effectively, ensuring your client terminates connections that exceed desired time limits.

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This lesson presents a technique for timing out network connections that take too long to finish on the client side. So, if the client does not receive a response from the server in the desired time, it closes the connection.

Coding example

The timeoutClient.go source file, without the import block, illustrates the technique.

Go (1.19.0)
package main
var myUrl string
var delay int = 5
var wg sync.WaitGroup
type myData struct {
	r   *http.Response
	err error
}

In the code above, we define global variables and a structure that are going to be used in the rest of the program.

Go (1.19.0)
func connect(c context.Context) error {
	defer wg.Done()
	data := make(chan myData, 1)
	tr := &http.Transport{}
	httpClient := &http.Client{Transport: tr}
	req, _ := http.NewRequest("GET", myUrl, nil)
	go func() {
		response, err := httpClient.Do(req)
		if err != nil {
			fmt.Println(err)
			data <- myData{nil, err}
			return
		} else {
			pack := myData{response, err}
			data <- pack
		}
	}()
	select {
	case <-c.Done():
		tr.CancelRequest(req)
		<-data
		fmt.Println("The request was canceled!")
		return c.Err()
	case ok := <-data:
		err := ok.err
		resp := ok.r
		if err != nil {
			fmt.Println("Error select:", err)
			return err
		}
		defer resp.Body.Close()
		realHTTPData, err := io.ReadAll(resp.Body)
		if err != nil {
			fmt.Println("Error select:", err)
			return err
		}
		// Although fmt.Printf() is used here, server processes
		// use the log.Printf() function instead.
		fmt.Printf("Server Response: %s\n", realHTTPData)
	}
	return nil
}
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