If the Go compiler was twice as fast, I wouldn't really notice.
If the Go linker was twice as fast, that would be a minor convenience, sometimes.
I wouldn't expect much more that twice, maybe thrice at the very outside. And it'd be a long journey to get there with bugs and such to work through. The blow-your-socks-off improvements come from when you start with scripting languages. Go may be among the slower compiled languages, but it's still a compiled language with performance in the compiled-language class; there's not a factor of 10 or 20 sitting on the table.
But having another implementation could be useful on its own merits. I haven't heard much about gccgo lately, though the project [1] seems to be getting commits still. A highly-compatible Go compiler that also did a lot of compile-time optimizations, the sort of code that may be more fun and somewhat more safe to write in Rust (though I would perceive that the challenge of such code is for the optimizations themselves to be correct rather than the optimization process not crashing, and Rust's ability to help with that is marginal). The resulting compiler would be slower but might be able to create much faster executables.
If the Go linker was twice as fast, that would be a minor convenience, sometimes.
I wouldn't expect much more that twice, maybe thrice at the very outside. And it'd be a long journey to get there with bugs and such to work through. The blow-your-socks-off improvements come from when you start with scripting languages. Go may be among the slower compiled languages, but it's still a compiled language with performance in the compiled-language class; there's not a factor of 10 or 20 sitting on the table.
But having another implementation could be useful on its own merits. I haven't heard much about gccgo lately, though the project [1] seems to be getting commits still. A highly-compatible Go compiler that also did a lot of compile-time optimizations, the sort of code that may be more fun and somewhat more safe to write in Rust (though I would perceive that the challenge of such code is for the optimizations themselves to be correct rather than the optimization process not crashing, and Rust's ability to help with that is marginal). The resulting compiler would be slower but might be able to create much faster executables.
[1]: https://github.com/golang/gofrontend