update: directory structure

advfuncs/exercises/01-refactor/solution/main.go

@@ -0,0 +1,28 @@
+// 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"
+
+func main() {
+	fmt.Println(headerOf("gif"))
+}
+
+var headers = map[string]string{
+	"png": "\x89PNG\r\n\x1a\n",
+	"jpg": "\xff\xd8\xff",
+}
+
+func headerOf(format string) (header string) {
+	defer func() {
+		if header == "" {
+			panic("unknown format: " + format)
+		}
+	}()
+	return headers[format]
+}