下面的 Go 代码中，为什么第 17 行的 c.L.Lock() 不会一直等待锁？

各位大佬，下面的 Go 代码中，当主 Goroutine 执行到 c.Wait() 的时候，第 28 行的 c.L.Lock() 肯定执行了，那么当执行到第 17 行的 c.L.Lock()，为什么程序不会一直阻塞呢？

package main

import (
	"fmt"
	"sync"
	"time"
)

// a goroutine that is waiting for a signal, and a goroutine that is sending signals.
// Say we have a queue of fixed length 2, and 10 items we want to push onto the queue
func main() {
	c := sync.NewCond(&sync.Mutex{})
	queue := make([]interface{}, 0, 10)

	removeFromQueue := func(delay time.Duration) {
		time.Sleep(delay)
		c.L.Lock() // 这是第 17 行，执行到这里为什么不是一直阻塞等待锁？

		queue = queue[1:]

		fmt.Println("Removed from queue")

		c.L.Unlock()
		c.Signal() // let a goroutine waiting on the condition know that something has ocurred
	}

	for i := 0; i < 10; i++ {
		c.L.Lock() // 这是 28 行，critical section

		// When the queue is equal to two the main goroutine is suspend
		// until a signal on the condition has been sent
		length := len(queue)
		fmt.Println(length)
		for len(queue) == 2 {
			fmt.Println("wait signal")
			c.Wait() // 这是 36 行，等待 signal ，但是 removeFromQueue 为什么不会一直等待锁呢？
		}

		fmt.Println("Adding to queue")
		queue = append(queue, struct{}{})

		go removeFromQueue(10 * time.Second)

		c.L.Unlock()
	}
}