Return error if stack is empty

sliceQueue.go

@@ -1,8 +1,13 @@
 package main
 
+import "errors"
+
 // Helper functions for slices, to make them behave more like stacks
-func peek[T any](s []T) T {
-	return s[len(s)-1]
+func peek[T any](s []T) (T, error) {
+	if len(s) < 1 {
+		return *new(T), errors.New("Stack empty")
+	}
+	return s[len(s)-1], nil
 }
 
 func pop[T any](sp *[]T) T {