emacs100

(setq package-archives '(("gnu" . "https://elpa.gnu.org/packages/")
                         ("melpa" . "https://melpa.org/packages/")))

(setq package-archives '(("gnu" . "http://mirrors.tuna.tsinghua.edu.cn/elpa/gnu/")
                         ("melpa" . "http://mirrors.tuna.tsinghua.edu.cn/elpa/melpa/")))

(setq package-archives '(("gnu" . "http://mirrors.cloud.tencent.com/elpa/gnu/")
                         ("melpa" . "http://mirrors.cloud.tencent.com/elpa/melpa/")))