go version update

update-go.bash

function update-go() {
  release=$(curl --silent https://golang.org/doc/devel/release.html | grep -Eo 'go[0-9]+(\.[0-9]+)+' | sort -V | uniq | tail -1)
  os=$(uname -s | tr '[:upper:]' '[:lower:]')
  arch=$(case "$(uname -m)" in i*) echo '386' ;; x*) echo 'amd64' ;; *) echo 'armv61'; esac)

  curl --silent https://storage.googleapis.com/golang/$release.$os-$arch.tar.gz \
    | sudo tar -vxz --strip-components 1 -C $(dirname $(dirname $(which go)))
}