add go plugin

plugins/available/go.plugin.bash

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+cite about-plugin
+about-plugin 'go environment variables & path configuration'
+
+[ ! command -v go &>/dev/null ] && return
+
+export GOROOT=${GOROOT:-$(go env | grep GOROOT | cut -d'"' -f2)}
+pathmunge "${GOROOT}/bin"
+export GOPATH=${GOPATH:-"$HOME/.go"}
+pathmunge "${GOPATH}/bin"