10x seems extreme. ESR went from 14k lines in Python to 21k in Go.
http://www.catb.org/~esr/reposurgeon/GoNotes.html
I have not had a chance to learn or use a language like Go. But production use of Python, including building large code bases is real. We do resort to numba, cython or using Python API to compiled code.
I'm now involved in converting large codebases from SAS to Python. I don't think I will have the luxury of choosing another language like Go, for a number of reasons.