go中使用多个返回值的惯用错误和值顺序

When creating a func that returns both an error and a result, which order should they be in? I've seen examples of both, and not sure where to look to confirm the idiomatic style.

should it be:

// a
func funcName(n int) (error, int) {}

// or b
func funcName(n int) (int, error) {}

As pointed out by @Gavin above in the comments :

If you look here, you will see By convention, errors are the last return value and have type error, a built-in interface.

As can be seen in the standard lib.