Add min function

Main.go

@@ -43,6 +43,13 @@ func max(a, b int) int {
 	return b
 }
 
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
 func date(year int, month time.Month, day int) time.Time {
 	return time.Date(year, month, day, 0, 0, 0, 0, time.Local)
 }