You wouldn't use an alignment-based style, but a block-based one instead:

  some_function(
      arg1,
      arg2,
      arg3,
      arg4,
      arg5,
      arg6,
  );

(I don't know what Go idiom says here, this is just a more general solution.)

You should NOT do such alignment anyway, because if you rename "some_function" to "another_function", then you will lose your formatting.

Instead, format arguments in a separate block:

    some_function(
        arg1, arg2, arg3, arg4,
        arg5, arg6);

When arguments are aligned in a separate block, both spaces and tabs work fine.

My own preference is tabs, because of less visual noise in code diff [review].

In an ideal world, I'd think you would put a "tab stop" character before arg1, then a single tab on the following line, with the bonus benefit that the formatting would survive automatic name changes and not create an indent-change-only line in the diff. Trouble being that all IDEs would have to understand that character, and compilers would have to ignore it (hey, ASCII has form feed and vertical tab that could be repurposed...).