How to enable TLS SNI using boost::beast

First include the required header:

#include <openssl/ssl.h>

Once you have initialized the boost::beast::ssl_stream, add the following code (with host being a std::string containing the hostname to connect to such as api.ipify.org):

if(!SSL_set_tlsext_host_name(stream.native_handle(), host.c_str())) {
    beast::error_code ec{static_cast<int>(::ERR_get_error()), net::error::get_ssl_category()};
    throw beast::system_error{ec};
}

Original source: boost::beast official HTTPS client example