Add hello package with tests

hello/go.mod

@@ -0,0 +1,3 @@
+module hello
+
+go 1.17

hello/hello.go

@@ -0,0 +1,33 @@
+package main
+
+import "fmt"
+
+const spanish = "Spanish"
+const french = "French"
+
+const englishHelloPrefix = "Hello, "
+const spanishHelloPrefix = "Hola, "
+const frenchHelloPrefix = "Bonjour, "
+
+func Hello(name string, language string) string {
+	if name == "" {
+		name = "World"
+	}
+
+	return greetingPrefix(language) + name
+}
+
+func greetingPrefix(language string) (prefix string) {
+	switch language {
+	case french:
+		prefix = frenchHelloPrefix
+	case spanish:
+		prefix = spanishHelloPrefix
+	default:
+		prefix = englishHelloPrefix
+	}
+	return
+}
+func main() {
+	fmt.Println(Hello("world", ""))
+}

hello/hello_test.go

@@ -0,0 +1,28 @@
+package main
+
+import "testing"
+
+func TestHello(t *testing.T) {
+	assertCorrectMessage := func(t testing.TB, got, want string) {
+		t.Helper()
+		if got != want {
+			t.Errorf("got %q want %q", got, want)
+		}
+	}
+
+	t.Run("saying hello to people", func(t *testing.T) {
+		got := Hello("Chris", "")
+		want := "Hello, Chris"
+		assertCorrectMessage(t, got, want)
+	})
+	t.Run("empty string defaults to 'World'", func(t *testing.T) {
+		got := Hello("", "")
+		want := "Hello, World"
+		assertCorrectMessage(t, got, want)
+	})
+	t.Run("in Spanish", func(t *testing.T) {
+		got := Hello("Elodie", "Spanish")
+		want := "Hola, Elodie"
+		assertCorrectMessage(t, got, want)
+	})
+}