run goimports automatically when saving Go code

autogoimports.py

# put this file in $HOME/.config/sublime-text-3/Packages

from sublime import *
from sublime_plugin import *

from os import environ
from subprocess import Popen, PIPE


class AutoGoimports(ViewEventListener):
    def on_pre_save(self):
        self.view.run_command("goimports")


class GoimportsCommand(TextCommand):
    # edit if necessary
    goimports = '{HOME}/go/bin/goimports'.format(**environ)
    gofmt = '/usr/local/go/bin/gofmt'

    def run(self, edit):
        if not self.view.settings().get('syntax').endswith("Go.sublime-syntax"): return
        region = Region(0, self.view.size())
        content = self.view.substr(region)
        command = '{} | {} -s'.format(self.goimports, self.gofmt)
        with Popen(command, shell=True, universal_newlines=True, stdin=PIPE, stdout=PIPE, stderr=PIPE) as p:
            stdout, stderr = p.communicate(content, 2)
            if stderr: error_message(stderr.replace('<standard input>:', '')[:400])
            elif stdout != content: self.view.replace(edit, region, stdout)