add: questions and exercises for the if statement

11-if/exercises/06/solution2/main.go

@@ -0,0 +1,39 @@
+// 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"
+	"os"
+	"strings"
+)
+
+func main() {
+	args := os.Args
+
+	if len(args) != 2 || len(args[1]) != 1 {
+		fmt.Println("Give me a letter")
+		return
+	}
+
+	s := args[1]
+	if strings.IndexAny(s, "aeiou") != -1 {
+		fmt.Printf("%q is a vowel.\n", s)
+	} else if s == "w" || s == "y" {
+		fmt.Printf("%q is sometimes a vowel, sometimes not.\n", s)
+	} else {
+		fmt.Printf("%q is a consonant.\n", s)
+	}
+
+	// Notice that:
+	//
+	// I didn't use IndexAny for the else if above.
+	//
+	// It's because, calling a function is a costly operation.
+	// And, this way, the code is simpler.
+}