This is a simple Go program, which extracts Go routine ID (an uint64 number) from the Go runtime internals.

Such obtaining of Go routine ID is highly discouraged by the Go authors and maintainers. It's intentionally hidden since in most cases building logic, based on knowing the current Go routine ID, is a bad idea. It often leads to a tangled, hard to understand and debug, code.

However, in some cases it's still needed. For experienced developers, who know what they do, it may be worth knowing the current Go routine ID. That's why this project is here.

I won't pretend I've invented something brand new here. All the code here is a result of my reading of the Go 1.23 runtime sources and googling around. There are several other projects on GitHub, where obtaining of the Go routine ID is implemented in a similar way. In all those projects, they provide some additional functionality around it.

But I don't need all those fancy features built around knowing the current Go routine ID. All I need is a fast and reliable way to obtain the ID as a number. I'll build all the logic around that on myself, if it's needed.

So I dived deep inside the Go 1.23 runtime sources and learned how it works with Go routines. Then, I found implementations of runtime·setg and implemented corresponding ·getg functions in Go Assembler for amd64 and arm64. For now, those are all architectures I need. In the future I might add more, if needed.

And then, knowing the pointer of the g object, I found a way to automatically find an offset of the goid field, using reflection and a few more functions from the Go runtime, which give me information about all the types in the program, and a way to resolve them into the reflect.Type objects.

That's it. Feel free to use this code, but do it only if you really know what you're doing. You've been warned.