Refactor: pull common parts of Get and Post to a private method
Refactor: pull common parts of Get and Post to a private method

isucon/isucon6-final,matsuu/isucon6-final,matsuu/isucon6-final,matsuu/isucon6-final,matsuu/isucon6-final,isucon/isucon6-final,matsuu/isucon6-final,isucon/isucon6-final,isucon/isucon6-final,matsuu/isucon6-final,isucon/isucon6-final,isucon/isucon6-final,isucon/isucon6-final,isucon/isucon6-final,matsuu/isucon6-final,matsuu/isucon6-final