// method is one that typically does not involve a request body.
// This is used by the Transport (via
// transferWriter.shouldSendChunkedRequestBody) to determine whether
// we try to test-read a byte from a non-nil Request.Body when
// Request.outgoingLength() returns -1. See the comments in
// shouldSendChunkedRequestBody.
func requestMethodUsuallyLacksBody(method string) bool {
	switch method {