curl does not support http2 on mac
The Homebrew team recently removed all options for the curl formula, but the curl-openssl formula has HTTP/2 enabled.
brew install curl-openssl
By default, curl is not compiled with nghttp2. As explained in this article, you need to recompile it passing the --with-nghttp2 flag and link it (to replace the original curl shipped with Mac OS X.
# install cURL with nghttp2 support$ brew install curl --with-nghttp2# link the formula to replace the system cURL$ brew link curl --force# now reload the shell