You say that, but I find that a lot harder to read (and using `e` notation) than just the number - and readability / clarity is more important than cleverness, especially in Go.
10_000_000 can be read, 5 * (1000**4) and 1e7 has to be decoded. By me anyway, I'm just an average developer that never did well in maths - and you have to write code for the average developer, not for yourself and not for the top 10% smartest people.
Not sure about go, but you can do this in C as a compile-time constant:
#define foo 1.34E8
Maybe go would benefit from a pre-processor? Though it can be somewhat byzantine in C (and result in very unpredictable final source, if abused), it's very helpful to have a complete functional language available for code transformation. It might help go in some cases, too.
I know we have scientific-notation integer literals, but it's not the same thing, especially when trying to calculate e.g. Mebibytes.