We knew it was a bad idea at the time it was standardized in the 1990s, but politics — and the inevitable allure of a very convenient sounding (but very bad) idea — meant that the bad idea won.

Funny enough, while Java has deprecated their version of thread cancellation for the same reasons, Haskell still has theirs. When you’re writing code in IO, you have to be prepared for async cancellation anywhere, at any time.

This leads to common bugs in the standard library that you really wouldn’t expect from a language like Haskell; e.g. https://github.com/haskell/process/issues/183 (withCreateProcess async exception safety)

If you don’t use the system resolver, you have to glue into the system’s configuration mechanism for resolvers somehow … which isn’t simple — for example, there’s a lot of complex logic on macOS around handling which resolver to use based on what connections, VPNs, etc, are present.

And the there’s nsswitch and other plugin systems that are meant to allow globally configured hooks plug into the name resolution path.

POSIX can specify a new version of DNS resolution.

libcs can add extensions, allowing applications to detect when they are targeting those systems and use them.

Applications on Linux and Windows can bypass libc.

The golang team also thought DNS clients were simple, and it led to almost ten years of difficult to debug panics in Docker, Mesos, Terraform, Mesos, and countless other services and CLI tools written in Go. (Search "cannot unmarshal DNS message" and marvel at the thousands of forum threads and GitHub issues that all bottom out at Go implementing the original DNS spec and not following later updates.)