update: directory structure

advfuncs/exercises/01-refactor/main.go

@@ -0,0 +1,33 @@
+package main
+
+import "fmt"
+
+// ---------------------------------------------------------
+// EXERCISE: Refactor
+//
+//   In the headerOf function, instead of using a switch,
+//   use a map. Declare it at the package-level.
+//
+// RESTRICTION
+//
+//   For panicking, use a deferred function and a named param.
+//
+// EXPECTED OUTPUT
+//
+//   Please run the solution.
+//
+// ---------------------------------------------------------
+
+func main() {
+	fmt.Println(headerOf("gif"))
+}
+
+func headerOf(format string) string {
+	switch format {
+	case "png":
+		return "\x89PNG\r\n\x1a\n"
+	case "jpg":
+		return "\xff\xd8\xff"
+	}
+	panic("unknown format: " + format)
+}