Question: I have 1.7 version of golang and I want to update golang to 1.8 from command prompt. Uninstalling and Installing it again is always an option, but can I update it using commands on Windows 8.1?

Answer: 
I think that GVM could be a good option for that. GVM is an interface to manage Go versions in your computer. It allows you to change the Go version and even installing/uninstalling different golang versions by command prompt.

You can install a new version by typing:

```
gvm install go1.4 -B
gvm use go1.4
export GOROOT_BOOTSTRAP=$GOROOT
gvm install go1.5

```

Or even get a list of golang versions installed in your computer:

```
gvm list

```

More information can be found on their website: <https://github.com/moovweb/gvm>
A simple way is to use the update-golang script:

```
git clone https://github.com/udhos/update-golang
cd update-golang
sudo ./update-golang.sh

```