Libmagic can not share handles across threads safely

[unclebadtouches]

I'm getting a crash in libmagic when using this library with multiple goroutimes. I suspect the reason is because this library keeps a single global handle that is used for all libmagic calls. A quick google search tells me that libmagic handles cannot be shared across threads.

Perhaps a better way to deal with this would be to wrap the libmagic handle as an opaque object that is passed back to the caller from Open(). Close() would also need a receiver or take an opaque handle as an argument.

[joeshaw]

While I haven't seen crashes, I've seen similar thread-safety issues, like getting back "image/jpegimage/jpeg" for a call to TypeByBuffer.

[rakyll]

We can proxy all calls thorough an operating system thread locked goroutine or update the samples that users are supposed to use runtime.LockOSThread.

[joeshaw]

I worked around it by wrapping my calls to TypeByBuffer in a mutex. Adding that to the library is another possible option, though it limits throughput.