kmutex lock is not exclusive.

[kkkiio]

Ⅰ. Issue Description

cleanup goroutine may delete the lock key from m.keys when the lock is not released, and then the lock is not exclusive.

Ⅱ. Describe what happened

goroutine 2 could acquire the lock when goroutine 1 is holding the lock.

Ⅲ. Describe what you expected to happen

goroutine 2 should be blocked until goroutine 1 release the lock.

Ⅳ. How to reproduce it (as minimally and precisely as possible)

func TestKMutexClean(t *testing.T) {
	m := New()
	var resource atomic.Int32
	c2 := make(chan struct{})
	done := make(chan struct{})
	go func() {
		time.Sleep(57 * time.Second)
		m.Lock("key")
		defer m.Unlock("key")
		if !resource.CompareAndSwap(0, 1) {
			panic("init error")
		}
		time.Sleep(4 * time.Second)
		close(c2)
		time.Sleep(1 * time.Second)
		if !resource.CompareAndSwap(1, 0) {
			panic("lock is not exclusive")
		}
	}()
	go func() {
		<-c2
		m.Lock("key")
		defer m.Unlock("key")
		if !resource.CompareAndSwap(0, 2) {
			panic("resource is used by other")
		}
		close(done)
	}()
	<-done
}