https://play.golang.org/ isn't a "real" REPL but it serves the same purpose for me in most cases. You can write a few quick lines just to test a theory e.g. "What happens if I pass this function this weird input?" or "Will this regexp function do what I think it does?"
The one that has seemed reasonable last I checked, was gore [1]. Then, you might want to check out the Golang Jupyter kernel as well (gophernotes [2]), which mentions gore as an inspiration.
