Golang通道在接收值之前死锁

Question

I'm not understanding why this doesn't work https://play.golang.org/p/_ALPii0pXV6 but this https://play.golang.org/p/vCOjAr-o54e works.

As I understand the goroutine asynchronously sends to value true to a and 12 to b. While in the main function, a is blocked, until it receives a value. Why is it that when I rearrange it to have b is blocked before a, it results in a deadlock?

Answer 1

Go channels are unbuffered by default. That means that it cannot send on a channel until the receiver is reading the channel. This is actually the Go preferred mode. It's more efficient than buffered channels in most cases.

What that means for your first code is that the goroutine cannot proceed to write to channel b until it completes the write to channel a. It cannot do that until the main goroutine reads a.