regexp

为什么使用regexp无法进行前向断言 img src="http://www.baidu.com/a.jpg" r, _ := regexp.Compile(`(?=img src=").+jpg`) 为啥吗报错呢。。runtime错误 panic: runtime error: invalid memory address or nil pointer dereference [signal 0xb code=0x1 addr=0x74 pc=0x8895d] goroutine 1 [running]: sync/atomic.CompareAndSwapUint32() /usr/local/go/src/pkg/sync/atomic/asm_amd64.s:14 +0xd sync.(*Mutex).Lock(0x74) /usr/local/go/src/pkg/sync/mutex.go:43 +0x35 regexp.(*Regexp).get(0x0, 0x101c81e8) /usr/local/go/src/pkg/regexp/regexp.go:178 +0x2a regexp.(*Regexp).doExecute(0x0, 0x0, 0x0, 0x210235000, 0x62, ...) /usr/local/go/src/pkg/regexp/exec.go:323 +0x35 regexp.(*Regexp).Find(0x0, 0x210235000, 0x62, 0x62, 0x210237000, ...) /usr/local/go/src/pkg/regexp/regexp.go:653 +0x80 main.MatchImage() /Users/whispermemory/Desktop/testimgsrc.go:23 +0x109 main.main() /Users/whispermemory/Desktop/testimgsrc.go:28 +0x18