Calling fork in a go program

I recently read the popular post about Redis architecture. It had a chapter about forking - the process of how they create a disk backup of the in-memory database contents. The chapter addresses some same system programming topics as the linux-insides book I've been glancing over recently.

As the article points out, the POSIX fork system call creates a duplicate of the calling process but does not copy the memory pages. If the parent or any child process access a memory page, it points to the read-only shared memory until the process changes any values of that page. The calling process then gets a writable copy of the accessed memory pages (copy-on-write).

DALL·E 2 did not know how to draw a go gopher but close enough!

Only single-threaded applications support fork, but I still decided to try it out on a go app. Go runtime does not support fork due to go programs being multithreaded and other reasons I don't even try to understand. There is a ForkExec call in the standard library that first forks but then runs exec, replacing everything, including the runtime.

As a curiosity, a go program can be forked but works only in trivial cases. I'm unsure what happens under the hood, TBH but seems to work as expected. Here is an example gist.

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