When your compiler is doing interprocedural optimizations like inlining (which Go's does), then changing an upstream dependency generally requires that all downstream dependencies be recompiled as well. So incremental recompilation isn't a panacea, and I think the Go designers made the right choice in striving to make compilation fast.

Of course, you can do something like incremental compilation only at -O0 with no inlining, which is what I suspect we'll end up doing in Rust (the relevant bug is [1]).

[1]: https://github.com/mozilla/rust/issues/2369