Advanced Techniques in Go Programming/

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Setting the Timeout Period on the Client Side

Setting the Timeout Period on the Client Side

Let’s learn how to set the timeout period on the client side.

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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.

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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.

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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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