golang编译器错误：无法加载软件包：软件包主要：/ home / ubuntu / workspace / Go中没有可构建的Go源文件

I am attempting to compile a go program. The code is a small x11 window manager, found HERE. (The code is 98 lines, too long to post here)

Here is the command I run, on x86-64 Ubuntu:

GOOS=linux GOARCH=386 go build littlewm.go

This command works fine on other files in the same directory. However, when I try to compile this one, I get the following error:

can't load package: package main: no buildable Go source files in /home/ubuntu/workspace/Go

This does not involve the gopath variable, as I have successfully compiled other programs in the same directory. I have a suspicion it involves the code itself or some option I am lacking. As such, this is not really a duplicate of an existing question and is quite possibly unique, since I am not getting the answer I want from other similar questions. Any help is appreciated greatly.

Thanks!