Download a File from a URL

This post shows how you can download a file in Go from a URL. We use the std lib (standard library) http.Get() [docs] and io.Copy() [docs] functions to help us with this. This function should be efficient as it will stream the data into the file, as opposed to downloading it all into memory, then to file.

The file will be saved in the same directory as your program.

We also show an alternative below if you want to take the filename from the URL.

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package main

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

func main() {

	fileUrl := "https://gophercoding.com/img/logo-original.png"

	// Download the file, params:
	// 1) name of file to save as
	// 2) URL to download FROM
	err := DownloadFile("saveas.png", fileUrl)
	if err != nil {
		fmt.Println("Error downloading file: ", err)
		return
	}

	fmt.Println("Downloaded: " + fileUrl)
}

// DownloadFile will download from a given url to a file. It will
// write as it downloads (useful for large files).
func DownloadFile(filepath string, url string) error {

	// Get the data
	resp, err := http.Get(url)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	// Create the file
	out, err := os.Create(filepath)
	if err != nil {
		return err
	}
	defer out.Close()

	// Write the body to file
	_, err = io.Copy(out, resp.Body)
	return err
}

golang download a file from url to local

Alternative Filename

In our example above, you needed to provide it with a file name to save as - but we can replace this, if we want, to use the original filename in the url. We’ve added a line to work out the filename from the url: path.Base(resp.Request.URL.String()).

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func DownloadFile(url string) error {

	// Get the data
	resp, err := http.Get(url)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	// Create the file
	filepath := path.Base(resp.Request.URL.String())
	out, err := os.Create(filepath)
	if err != nil {
		return err
	}
	defer out.Close()

	// Write the body to file
	_, err = io.Copy(out, resp.Body)
	return err
}

Download a File from a URL

Alternative Filename

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