Go isn't a competitor to C or C++. I don't know where that idea even comes from. Go is competing with Java and web languages.
Rust is the only real competitor, but given the sheer amount of existing C and C++ code, the idea that they will become legacy languages any time soon is pretty out to lunch.
A lot of command line tooling is being written in Go along with systems software (like basically all of container land). Maybe some of these would have otherwise been written in C or C++. For example, if you use the Azure storage GUI to manage storage the underlying "thing" that copies data from your filesystem to azure storage is written in Go and that's why it works on Windows, Linux, MacOS. C++ is somewhat more portable than C so maybe something like that would have been written in C++? Who knows? But Go is definitely showing up in all sorts of native, command-line stuff. And Rob Pike - one of the people who developed Go - intended it to be a new home for C++ developers as well.
