When Undertow is used to implement HTTP/2 protocol, supporting  5G 3GPP SBI (Service Based Interfaces) as specified in

3GPP TS 29.500 (v17.2.0) Technical Realization of Service Based Architecture, the following HTTP/2 connection management should be supported:

5.2.6       HTTP/2 connection management

The 3GPP NF shall support gracefully shutdown of a HTTP/2 connection by sending a GOAWAY frame with "Error Code" field set to "NO_ERROR (0x0)". The HTTP connection should remain "open" (by the sender and receiver of GOAWAY frame) until all in-progress streams numbered lower or equal to the last stream identifier indicated by the "Last-Stream-Id" field in the GOAWAY frame are completed. See clause 6.8 of IETF RFC 7540 [7].

The HTTP/2 GOAWAY frame requirements are specified in RFC7540 Hypertext Transfer Protocol Version 2 (HTTP/2)  https://tools.ietf.org/html/rfc7540 Chpt. 6.8. GOAWAY

Moreover, it is desirable that the underneath HTTP/2 connection is public for applications built on the The Buildr API, e.g. access to  XnioWorker, ByteBufferSlicePool, ChannelListener and StreamConnection   

in addition to HttpServerExchange.