reorganize: interfaces section

interfaces/03-nonstructs/book.go

@@ -0,0 +1,20 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import "fmt"
+
+type book struct {
+	title string
+	price float64
+}
+
+func (b book) print() {
+	// b is a copy of the original `book` value here.
+	fmt.Printf("%-15s: $%.2f \n", b.title, b.price)
+}