Panic when pressure testing

[qiantaossx]

The golang stack as following:

goroutine 15576 [running]:
math/rand.(*rngSource).Uint64(...)
	/usr/local/go/src/math/rand/rng.go:249
math/rand.(*rngSource).Int63(0xc000711ba0?)
	/usr/local/go/src/math/rand/rng.go:234 +0x85
math/rand.(*Rand).Int63(...)
	/usr/local/go/src/math/rand/rand.go:96
math/rand.(*Rand).Int(...)
	/usr/local/go/src/math/rand/rand.go:114
srs-proxy/rtmp.(*Handshake).WriteC1S1(0xc000711e58, {0x81aa00, 0xc0002103e8})
	/build/rtmp/rtmp.go:60 +0x66
main.(*RTMPConnection).serve(0xc00019a160, {0x81db78, 0xc00219b7a0}, 0xc0002103e8)
	/build/rtmp.go:163 +0x28f
main.(*srsRTMPServer).Run.func1.1({0x81db78, 0xc00219b7a0}, 0xc0002103e8)
	/build/rtmp.go:102 +0x129
created by main.(*srsRTMPServer).Run.func1 in goroutine 11
	/build/rtmp.go:87 +0x9c

read basic header
srs-proxy/rtmp.(*Protocol).readBasicHeader
	/build/rtmp/rtmp.go:667
srs-proxy/rtmp.(*Protocol).ReadMessage
	/build/rtmp/rtmp.go:315
main.(*RTMPConnection).serve.func3.1
	/build/rtmp.go:357
main.(*RTMPConnection).serve.func3
	/build/rtmp.go:368
runtime.goexit
	/usr/local/go/src/runtime/asm_amd64.s:1700
read basic header
read message
main.(*RTMPConnection).serve.func3.1
	/build/rtmp.go:359
main.(*RTMPConnection).serve.func3
	/build/rtmp.go:368