I recently did something similar but in Rust. Any chance you found a way to update posts on Medium? Also, were you ever able to get hashnode update to work? It always returns 502 bad gateway whenever I try.
Cody Bontecou bugger, has hoped I was just doing something foolish with GraphQL. There's a few problems with their API- even got a server callstack once. Tried contacting them via hello@hashnode (or was it help@?) and never got a reply. Oh, well...