Add day four Bingo player

four/main.go

@@ -0,0 +1,27 @@
+package four
+
+import "fmt"
+
+type Four struct {
+	bingo bingo
+}
+
+func Init(filepath string) *Four {
+	four := &Four{
+		bingo: bingo{},
+	}
+
+	four.bingo.read(filepath)
+	return four
+}
+
+func (d *Four) Answer() string {
+	score, call := d.bingo.play()
+	return fmt.Sprintf("The winning score is %d on call %d. Final score %d", score, call, score*call)
+}
+
+func (d *Four) FollowUp() string {
+	d.bingo.reset()
+	score, call := d.bingo.slowPlay()
+	return fmt.Sprintf("The last winning score is %d on call %d. Final score %d", score, call, score*call)
+}