If you can manage to register a constructor function, you can get your code executing without the target code having to call anything. In GCC, adding __attribute__((constructor)) before a no-argument function returning void works. I don't have a specific suggesiton for how to make this work in Go, although if you can add arbitrary C-compatible attributes and use the platform linker, setting the constructor attribute should just work.

In C++, constructors on static global objects get run automatically (via this mechanism), so if Go has something similar, that would work. (Stable) Rust goes out of its way to make you not able to do this because it's an anti-pattern, but there's a stupid trick if you can assume GNU: https://github.com/geofft/redhook/blob/master/src/lib.rs#L34...

Alternatively, you can just write an __attribute__((constructor)) function in C that calls an exported Go function that in turn calls `go backdoor()`, and link them all together.