net/http2: if the only stream in a connection times out, prevent re-use

This commit mitigates some raciness which can occur when an established
connection fails. Without it, the connection can continue to be drawn
from the connection pool, leading to subsequent requests failing.

Fixes golang/go#59690

http2/transport.go

@@ -1444,8 +1444,22 @@ func (cs *clientStream) writeRequest(req *http.Request) (err error) {
 			respHeaderRecv = nil
 			respHeaderTimer = nil // keep waiting for END_STREAM
 		case <-cs.abort:
+			// If this was the only active stream, mark the connection
+			// as not for re-use in order to address raciness if the caller
+			// tries to call closeIdleConnections() before the stream has been
+			// removed
+			if len(cc.streams) == 1 {
+				cc.doNotReuse = true
+			}
 			return cs.abortErr
 		case <-ctx.Done():
+			// If this was the only active stream, mark the connection
+			// as not for re-use in order to address raciness if the caller
+			// tries to call closeIdleConnections() before the stream has been
+			// removed
+			if len(cc.streams) == 1 {
+				cc.doNotReuse = true
+			}
 			return ctx.Err()
 		case <-cs.reqCancel:
 			return errRequestCanceled