We need an init function in order to process upgrade instructions
for protocols like WebSockets, but also to request an active receive
mode for long-polling connections, both of which will be implemented
at a later time.
Crashes can happen if we close the connection too fast, leading to
controlling_process returning {error, closed} instead of ok. This can
happen when we receive bad requests, reply with 404 Not Found and more.
Simply do not match the return value of controlling_process to avoid this.
