This will send a request to the server using the HTTP request method
method and the selector url. If the body argument is
present, it should be a string of data to send after the headers are finished.
The header Content-Length is automatically set to the correct value.
The headers argument should be a mapping of extra HTTP headers to send
with the request.
Send an RFC 822-style header to the server. It sends a line to the
server consisting of the header, a colon and a space, and the first
argument. If more arguments are given, continuation lines are sent,
each consisting of a tab and an argument.