Hello world Assembly x64 (WinAPI)

; Hello world program
; Language: x86-64 (AMD64) Assembly
; Library: Windows API 64-bit

global _start

extern GetStdHandle
extern WriteFile

section .text
_start:
    mov rcx, -11
    sub rsp, 8
    mov rbx, rsp
    sub rsp, 32
    call GetStdHandle
    add rsp, 32
    push dword 0
    mov r9, rbx
    mov r8, message_length
    mov rdx, message
    mov rcx, rax
    sub rsp, 40
    call WriteFile
    add rsp, 56
    xor rax, rax
    ret

section .data
    message db 'Hello world!', 0xD, 0xA
    message_length equ $ - message