This is a simple tutorial that also provides a code example on doing a x64 xor encoder and loader for shellcode. hello_world, shell with setreuid, and portbind shellcode examples are provided.
You can download it from the following link: https://packetstormsecurity.com/files/download/104576/x64_xor_encoder.txt
Source: https://packetstormsecurity.com/files/104576/Simple-x64-XOR-Shellcode-Encoder-Loader.html