channel怎么实现线程安全

题目来源：腾讯

答案：

channel结构如下

  1. type hchan struct {
  2.     qcount   uint           // total data in the queue
  3.     dataqsiz uint           // size of the circular queue
  4.     buf      unsafe.Pointer // points to an array of dataqsiz elements
  5.     elemsize uint16
  6.     closed   uint32
  7.     elemtype *_type // element type
  8.     sendx    uint   // send index
  9.     recvx    uint   // receive index
  10.     recvq    waitq  // list of recv waiters
  11.     sendq    waitq  // list of send waiters
  13.     // lock protects all fields in hchan, as well as several
  14.     // fields in sudogs blocked on this channel.
  15.     //
  16.     // Do not change another G's status while holding this lock
  17.     // (in particular, do not ready a G), as this can deadlock
  18.     // with stack shrinking.
  19.     lock mutex
  20. }

在定义时结构中包含一个读写锁
当想往chan中发送数据或者是接收数据时都会先给chan上锁
所以channel是线程安全的