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: 
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.*"
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

```