加速国内Github访问
1 获取GitHub官方CDN地址
2 修改系统Hosts文件
3 刷新系统DNS缓存
由于某些原因，国内访问Github会异常缓慢，在clone仓库时甚至只有10k以下的速度，下载半天有时还会失败需要从头再来，甚是让人恼火。
本文介绍通过修改系统hosts文件的办法，绕过国内dns解析，直接访问GitHub的CDN节点，从而达到加速的目的。不需要科学上网，也不需要海外的服务器辅助。
1. 获取GitHub官方CDN地址
查询以下三个链接的DNS解析地址
- github.com
- assets-cdn.github.com
- github.global.ssl.fastly.net
记录下查询到的IP地址。
2. 修改系统Hosts文件
打开系统hosts文件(需管理员权限)。
路径：C:\Windows\System32\drivers\etc
在末尾添加三行记录并保存。(需管理员权限，注意IP地址与域名间需留有空格，notepad++在保存时会提示需要权限，自动切换成管理员模式打开)
# Copyright (c) 1993-2009 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host
# localhost name resolution is handled within DNS itself.
# 127.0.0.1 localhost
# ::1 localhost
192.30.253.112 github.com
151.101.72.133 assets-cdn.github.com
151.101.193.194 github.global.ssl.fastly.net
3 刷新系统DNS缓存
Windows+X 打开系统命令行（管理员身份）或powershell
运行 ipconfig /flushdns 手动刷新系统DNS缓存。
