There is a real practical problem with the dichotomy in Go unfortunately, where on the one hand a single threaded program is safe, but on the other hand no go programs are single threaded. More mitigations are coming and synctest for example is quite welcome and is already helping where we've tested it, but this stuff just feels like the same old whack-a-mole as e.g. fuzzing for other solutions. gvisors checklocks for example isn't tenable for us without hugely more investment as there are tons of cases it just can't handle (like inline funcs, which we have more than we ought to). You're right that it's different, though - data races are often much harder to discover, arrange and leverage.
We've witnessed memory corruption events (from plain go code), and it's raised real concerns even among our strongest advocates. Our most recent case was actually a false-positive, in that there was a real race on a map, but it so happened it would never have reached a data race - still it tore down a process in production, and this is good and bad on multiple fronts. It doesn't make the solution invalid, and no one should be throwing internet punches over it, but it's absolutely reasonable to be concerned about memory corruption cases in complex go programs. In general my advice for Go usage is to write small programs with low concurrency and small heaps, this manages associated risks well, both in terms of authorship and exposure when events come up. Small container sized things are probably fine, essentially, but many tens of gb of user data in heaps with hundreds of constantly changed kloc is a place to be genuinely concerned.
Reflecting back on the starting context, and this advice, they align. The compiler has no high value user data to corrupt, if it suffers memory corruption the bad cases have to be pretty lucky not to end up in sufficiently total failure as to cause true end user problems. The runtime is short lived and compartmentalized, and it's not in a highly adversarial environment - this is a fine fitting use case. In an attacker heavy situation like the font system though, essentially I'm almost ready to drop maybe one layer of sandboxing once it's implemented with stronger guarantees and had some appropriate testing. I'm not sure I'd be ready to say that with less safety guarantees.
