Go 1.27 improves HTTP/1 connection reuse when response bodies go unread

Go 1.27 automatically drains unread HTTP/1 response bodies to help reuse connections, the Go project explains in a technical post. Previously, closing a response with unread data caused the client to abandon the connection and pay connection setup costs again. The transport now drains data asynchronously for up to 50 ms or 256 KB. It skips draining when a response explicitly closes the connection. In the author's test, 100 status-check requests took approximately 710 milliseconds with Go 1.26 and approximately 150 milliseconds with Go 1.27. Those results came from one machine with HTTP/2 disabled; HTTP/2 does not have the same unread-body problem.