According to a quick GitHub search, “the connection is closed for writing”. 
This file (the first of two matches in the GitHub search) has 26 matches of read_only, I’d go read it in more detail. (Some of the matches are actually in the symbols outline on the right but still, at least 15 matches in the file from what I’ve seen.)
And this file (the second match) implies that the server “has sent GOAWAY and then replies, we get the replies but are closed for writing” which might be I don’t know, rate limit hit? Or maybe you have inadvertently opened it in HTTP2 streaming mode without the option to write to the connection (as one of the code matches implies)?
