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>
If using Chocolatey mode of upgrade as David suggested, there is a possibility that the GOPATH defined on your system may not match with the existing one (if you had set a custom path via manual install).
Chocolatey, will install the Go binaries under %USERPROFILE%/go/bin --> C:\Program Files\Go\bin
So please ensure the path and update your environment variables accordingly.

Installation message may look something like below, if the path changes.

"*Environment Vars (like PATH) have changed. Close/reopen your shell to
see the changes (or in powershell/cmd.exe just type `refreshenv`).
The upgrade of golang was successful.
Software installed as 'msi', install location is likely default.*"