panic: runtime error: index out of range

[rc452860]

panic: runtime error: index out of range

goroutine 19559173 [running]:
crypto/cipher.fastXORBytes(0xc42478d000, 0xc, 0xc, 0xc425406ff0, 0x766, 0xeff3, 0xc42577c740, 0x10, 0x10, 0xc42577c760)
/home/travis/.gimme/versions/go1.10.7.linux.amd64/src/crypto/cipher/xor.go:26 +0x12f
crypto/cipher.xorBytes(0xc42478d000, 0xc, 0xc, 0xc425406ff0, 0x766, 0xeff3, 0xc42577c740, 0x10, 0x10, 0x10)
/home/travis/.gimme/versions/go1.10.7.linux.amd64/src/crypto/cipher/xor.go:60 +0x8e
crypto/cipher.(*cfb).XORKeyStream(0xc4213da000, 0xc42478d000, 0xc, 0xc, 0xc425406ff0, 0x766, 0xeff3)
/home/travis/.gimme/versions/go1.10.7.linux.amd64/src/crypto/cipher/cfb.go:32 +0x1c2
github.com/rc452860/vnet/ciphers/ssstream.(*streamPacket).WriteTo(0xc42d4864e0, 0xc425406000, 0x1756, 0xffe3, 0x8faae0, 0xc421114f30, 0x0, 0x0, 0x0)
/home/travis/gopath/src/github.com/rc452860/vnet/ciphers/ssstream/cipher_packet.go:58 +0x204
github.com/rc452860/vnet/proxy/server.timedCopy(0x8fde60, 0xc42d4864e0, 0x8faae0, 0xc421114f30, 0x8fdfe0, 0xc42d207388, 0xb2d05e00, 0x0, 0x0, 0x0)
/home/travis/gopath/src/github.com/rc452860/vnet/proxy/server/shadowsocks.go:488 +0x4f5
github.com/rc452860/vnet/proxy/server.(*natmap).Add.func1(0x8fde60, 0xc42d4864e0, 0x8faae0, 0xc421114f30, 0x8fdfe0, 0xc42d207388, 0xc429a5a180, 0x0)
/home/travis/gopath/src/github.com/rc452860/vnet/proxy/server/shadowsocks.go:464 +0x85
created by github.com/rc452860/vnet/proxy/server.(*natmap).Add
/home/travis/gopath/src/github.com/rc452860/vnet/proxy/server/shadowsocks.go:463 +0xd1