Go lang request timeouts example, DialContext, context.WithTimeout, http.Client, http.NewRequestWithContext

timeouts.go

package main

import (
	"context"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"time"
)

// Connect timeout error:
//  panic: Cannot do request: Get http://localhost:3000: dial tcp: i/o timeout
// Request timeout error:
//  panic: Cannot do request: Get http://localhost:3000: context deadline exceeded
// Example output
//  2020/11/03 12:23:42 Do request
//  2020/11/03 12:23:43 Read body
//  2020/11/03 12:23:43 Read response took: 154.884µs
//  2020/11/03 12:23:43 {"ip":"*.*.*.*","country":"Ukraine","cc":"UA"}
func main() {
	const ConnectMaxWaitTime = 1 * time.Second
	const RequestMaxWaitTime = 5 * time.Second

	client := http.Client{
		Transport: &http.Transport{
			DialContext: (&net.Dialer{
				Timeout: ConnectMaxWaitTime,
			}).DialContext,
		},
	}

	ctx, cancel := context.WithTimeout(context.Background(), RequestMaxWaitTime)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, "https://api.myip.com", nil)
	if err != nil {
		log.Panicf("Cannot create request: %s\n", err)
	}

	log.Println("Do request")
	rsp, err := client.Do(req)
	if rsp != nil {
		defer rsp.Body.Close()
	}
	if e,ok := err.(net.Error); ok && e.Timeout() {
		log.Panicf("Do request timeout: %s\n", err)
	} else if err != nil {
		log.Panicf("Cannot do request: %s\n", err)
	}

	log.Println("Read body")
	startRead := time.Now()
	body, err := ioutil.ReadAll(rsp.Body)
	if err != nil {
		log.Panicf("Cannot read all response body: %s\n", err)
	}
	endRead := time.Now()
	log.Printf("Read response took: %s\n", endRead.Sub(startRead))

	log.Printf("%s\n", body)
}