panic: runtime error: invalid memory address or nil pointer dereference [signal 0xb code=0x1 addr=0x20 pc=0x40fe940]
goroutine 19 [running]: panic(0x4206540, 0xc82000e120) /usr/local/go/src/runtime/panic.go:481 +0x3e6 github.com/google/gopacket/tcpassembly/tcpreader.DiscardBytesToFirstError(0x0, 0x0, 0x0, 0x0, 0x0) /usr/local/go/src/github.com/google/gopacket/tcpassembly/tcpreader/reader.go:60 +0x60 github.com/google/gopacket/tcpassembly/tcpreader.DiscardBytesToEOF(0x0, 0x0, 0x0) /usr/local/go/src/github.com/google/gopacket/tcpassembly/tcpreader/reader.go:75 +0x38 main.(msrpStreamHandler).run(0xc821400000) /Users/xm/workgo/src/github.com/google/gopacket/examples/msrpassembly/main.go:55 +0x1ad created by main.(msrpStreamFactory).New /Users/xm/workgo/src/github.com/google/gopacket/examples/msrpassembly/main.go:90 +0x1a6
