code: func (l *State) Register(name string, f Function) {
  	l.PushGoFunction(f)
  	l.SetGlobal(name)
  }
docs: // Register sets the Go function f as the new value of global name. If
  // name was already defined, it is overwritten.
  //
  // http://www.lua.org/manual/5.2/manual.html#lua_register