Go 1.10 源码安装简单很多啊

Go 1.5 之后，由于实现了自举，需要先安装之前的版本，然后得配置 GOROOT_BOOTSTRAP 环境变量： ``` ERROR: Cannot find xxx/go1.4/bin/go. Set $GOROOT_BOOTSTRAP to a working Go tree >= Go 1.4. ``` Go 1.10 之后，不再需要配置该环境变量，能够自动找到，对新手越来越友好了！安装过程的日志输出简单很多 ``` Building Go cmd/dist using /usr/local/go1.9. Building Go toolchain1 using /usr/local/go1.9. Building Go bootstrap cmd/go (go_bootstrap) using Go toolchain1. Building Go toolchain2 using go_bootstrap and Go toolchain1. Building Go toolchain3 using go_bootstrap and Go toolchain2. Building packages and commands for linux/amd64. ```