add: ifaces testing

interfaces/18-testing/main.go

@@ -0,0 +1,40 @@
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+// For more tutorials  : https://learngoprogramming.com
+// In-person training  : https://www.linkedin.com/in/inancgumus/
+// Follow me on twitter: https://twitter.com/inancgumus
+
+package main
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+)
+
+func main() {
+	// resp, err := http.Get("https://inancgumus.github.com/x/rosie.jpg")
+	resp, err := http.Get("https://inancgumus.github.com/x/rosie.unknown")
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		return
+	}
+	defer resp.Body.Close()
+
+	file, err := os.Create("rosie.png")
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		return
+	}
+	defer file.Close()
+
+	n, err := io.Copy(file, pngReader(resp.Body))
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		return
+	}
+	fmt.Printf("%d bytes transferred.\n", n)
+}