func (s *threadSafeStack) Push(element interface{}) {
	s.Lock()
	defer s.Unlock()
	s.elements = append(s.elements, element)
}
Push pushes an element onto the top of this Stack.
package stack
import (
	"sync"
)
type threadSafeStack struct {
	sync.RWMutex
	elements []interface{}
}
func newThreadSafeStack() *threadSafeStack {
	return &threadSafeStack{}
}