Hi all,
Whether you use Easy Code or not, you can take advantage of the 64-bit include and library files available with the Easy Code package, which contains files for ASMC, FASM, JWASM, MASM, POASM and UASM (http://www.easycode.cat/English/Download.htm). ASMC, JWASM, POASM and UASM use the same include files than MASM.
On the other hand, GoAsm uses the Edgar Hansen's GoAsm Headers (https://1drv.ms/u/s!AtgCy-XywfO-hswt7RlbeWTxBgjjww).
Regards.