我要我觉得！ 我觉得对了，但是被结果打了脸

```go func main() { f4() } func f4() { m := make(map[string]int) var lock sync.RWMutex go func(m map[string]int, l sync.RWMutex) { for { time.Sleep(time.Second * 1) l.RLock() fmt.Println("token now is : ", m["a"]) l.RUnlock() } }(m, lock) for { time.Sleep(time.Nanosecond * 1) lock.Lock() m["a"] = rand.Int() lock.Unlock() } } ``` 讲道理没啥问题呀，怎么还会报读写冲突呢？能解此迷的绝对是牛人。 token now is : 1013340838 token now is : 1876733110 token now is : 166916850 fatal error: concurrent map read and map write goroutine 5 [running]: runtime.throw(0x80e8a1a, 0x21) /usr/local/go/src/runtime/panic.go:608 +0x6a fp=0x842c768 sp=0x842c754 pc=0x806b8fa runtime.mapaccess1_faststr(0x80d1960, 0x8448120, 0x80e408f, 0x1, 0x0) /usr/local/go/src/runtime/map_faststr.go:21 +0x34a fp=0x842c7a0 sp=0x842c768 pc=0x8054e4a main.f4.func1(0x8448120, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0) /root/go/test/tamp/main.go:31 +0x80 fp=0x842c7d0 sp=0x842c7a0 pc=0x80bee70 runtime.goexit() /usr/local/go/src/runtime/asm_386.s:1324 +0x1 fp=0x842c7d4 sp=0x842c7d0 pc=0x8091201 created by main.f4 /root/go/test/tamp/main.go:27 +0x62 goroutine 1 [runnable]: time.Sleep(0x1, 0x0) /usr/local/go/src/runtime/time.go:100 +0x110 main.f4() /root/go/test/tamp/main.go:36 +0x76 main.main() /root/go/test/tamp/main.go:21 +0x17 exit status 2