If you insert "browser" between "existing" and "implementation" then it's correct. Most libraries also support unencrypted HTTP/2. E.g. nghttp2 (as used here in node.js, and also used by others like apache and curl) supports unencrypted connections. My own library for C# (https://github.com/Matthias247/http2dotnet) does too. The Go library might be a little bit of a special case, as it actually supports it, but the required functions are (or at least were) not exposed in the standard libraries http package. They should however be available in the x/net/http2 package.
