Ben Hoyt's great write up of an AWK interpreter he wrote in Go, including an overview of the lexer, parser, interpreter, unit tests, and profiling for performance improvements.
Calls itself "an open source pastebin with runnable snippets and API". It's a nice and useful REPL environment for many langauges. More simple than repl.it
After writing a few programs in Go, I appreciate its simplicity and how easy it is to cross-complile and deploy simple programs, but I agree its type system is a bit *too* simple.