Panic: Failed to load system translations for 'en'

hahaha ok, but just in case.

Go plugin for jetbrains version 0.11.1295
and check that GOPATH is shown under Languages & Framworks -> Go -> Go Libraries

This is what I have in run config
Run kind: File
Filename: path to mattermost.go
Working directory: Path to cloned repo
Program arguments: -config=config.json

Hope it helps