Alan A. A. Donovan and Brian W. Kernighan, The Go Programming Language. Addison-Wesley, 2016, Chapter 1, Tutorial

Exercises 1.7, 1.8 and 1.9

Exercise 1.7: The function call io.Copy(dst, src) reads from src and writes to dst. Use it instead of ioutil.ReadAll to copy the response body to os.Stdout without requiring a buffer large enough to hold the entire stream. Be sure to chec the error result of io.Copy.

Exercise 1.8: Modify fetch to add the prefix http:// to each argument URL if it is missing. You might want to use strings.HasPrefix.

Exercise 1.9: Modify fetch to also print the HTTP status code, found in resp.Status.

My solution

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package main

import (
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"
)

func main() {
	for _, url := range os.Args[1:] {

		// Modification for Exercise 1.8.
		if !strings.HasPrefix(url, "http://") {
			url = "http://" + url
		}

		// Get `url` and store data in `resp`, whic is a struct with a
		// `Body` field that contains the server response as a readable
		// stream.
		resp, err_http := http.Get(url)
		if err_http != nil {
			fmt.Fprintf(os.Stderr, "fetch: %v\n", err_http)
			os.Exit(1)
		}

		// Original code provided in Section 1.5:
		// b, err := ioutil.ReadAll(resp.Body)

		// Modifications for Exercise 1.7 and 1.9.
		fmt.Println("Status:", resp.Status)
		_, err_copy := io.Copy(os.Stdout, resp.Body)
		resp.Body.Close()

		if err_copy != nil {
			fmt.Fprintf(os.Stderr, "fetch: reading %s: %v\n", url, err_copy)
			os.Exit(1)
		}
	}
}