def spawn(self, env=None, **kwargs):
      env = (env or os.environ).copy()
      env.update(self.env)
      return subprocess.Popen(self.cmdline, env=env, **kwargs)
:param dict env: A custom environment to launch the Go command in.  If `None` the current
dataset/ETHPy150Open pantsbuild/pants/contrib/go/src/python/pants/contrib/go/subsystems/go_distribution.py/GoDistribution.GoCommand.spawn