Golang daily question

2022-02-16 channel

• Give me a nil channel send data , Cause permanent obstruction
• From a nil channel receive data , Cause permanent obstruction
• To a closed channel send data , cause panic
• From a closed channel receive data , If the buffer is empty , Then return a zero value
• Unbuffered channel It's synchronous , And there's a buffer channel asynchronous

2022-02-17 sync.WaitGroup

func main() {
    
	const N = 10
	var wg = &sync.WaitGroup{
    }
	
	for i := 0; i < N; i++ {
    
		wg.Add(1)			// add 1 goroutine to WaitGroup
		go func(i int) {
    
			println(i)
			defer wg.Done()	//a goroutine finished
		}(i)
	}
	wg.Wait()				//wait util all goroutines finish
}

• function ： Wait for all threads to end
• wg.Wait() Will block , If there are still threads waiting
• wg.Add() Increase the number of threads that need to wait
• wg.Done() The waiting thread ends , namely wg.Add(-1)