fix warning [DeprecationWarning: The Buffer() and new Buffer()]

[snickerjp]

Description of changes:

warning detected.

• Node.js > 8

DeprecationWarning: The Buffer() and new Buffer() constructors are not recommended for use due to security and usability concerns. Please use the new Buffer.alloc(), Buffer.allocUnsafe(), or Buffer.from() construction methods instead.

ref. https://nodejs.org/en/docs/guides/buffer-constructor-deprecation/

fix this PR.