Comment by MartinodF

Say you have some code that does a request to an HTTP/1 dependency, and if it get an error response, just closes the connection without reading the response body.

Go 1.26 in practice never re-used that connection, it always established a new one because you can't reuse a connection which has a pending response ready to be read.

Go 1.27 will now consume the body for you, causing your application to re-use connections much more aggressively, bringing in potential edge cases (e.g. dependency is broken, connection is now permanently unusable, your app no longer recovers automatically).

To be clear, I'm very glad for the change and I had equivalent code in our in-house framework to do just that, but yeah it does change the behavior in a way that it could expose undetected issues.