This should follow the way you set any Environment variable with Powershell (as described in this article):
If you want it permanent (ie will apply for any future shell):
[Environment]::SetEnvironmentVariable("GOPATH", "C:\Your\Path", "User")
One thing to watch out for: when we used
SetEnvironmentVariableto create a new user- or machine-level environment variable that variable didn’t always show up when we ran this command in Windows PowerShell:
Get-ChildItem Env:
Or at least it didn’t show up until we restarted PowerShell. (Or started up a new instance of PowerShell.)
However, we could retrieve the value of the new variable at any time by using this command:
[Environment]::GetEnvironmentVariable("GOPATH","User")
If you want it for just the current shell, as mentioned in cmotley's answer and detailed in the same article:
$env:GOPATH = "C:\Your\Path"
As Jaykul comments, setting that line in your %UserProfile%\My Documents\WindowsPowerShell\profile.ps1 is the equivalent of an export in ~\.bashrc:
See "Windows PowerShell Profiles".
(There are actually 4 profiles, the one profile mentioned applies only to the current user, but affects all shells)