仅仅输出了第一行，第二行就报错

fatal error: all goroutines are asleep - deadlock!

goroutine 1 [semacquire]:
sync.runtime_Semacquire(0x5852f8)
    D:/Go/src/runtime/sema.go:56 +0x40
sync.(*WaitGroup).Wait(0x5852f0)
    D:/Go/src/sync/waitgroup.go:130 +0x6b
main.main()