My team at Google is wrapping up an effort to rewrite a large production system (almost) entirely in Go. I say "almost" because one component of the system -- a library for transcoding between image formats -- works perfectly well in C++, so we decided to leave it as-is. But the rest of the system is 100% Go, not just wrappers to existing modules in C++ or another language. It's been a fun experience and I thought I'd share some lessons learned.