Developers should use a recent version of Go for building and testing. We use the go toolchain for development, which you can get from the [Go downloads page](https://golang.org/doc/install). Geth is a Go module, and uses the [Go modules system](https://github.com/golang/go/wiki/Modules) to manage dependencies. Using `GOPATH` is not required to build go-ethereum.
If Geth is started with the `--pprof` option, a debugging HTTP server is made available on port 6060. Navigating to <http://localhost:6060/debug/pprof> displays the heap, running routines etc. By clicking "full goroutine stack dump" a trace can be generated that is useful for debugging.
Note that if multiple instances of Geth exist, port `6060` will only work for the first instance that was launched. To generate stacktraces for other instances, they should be started up with alternative pprof ports. Ensure `stderr` is being redirected to a logfile.