The Cancel method cancels the current blocking
request by closing the active HTTP connection associated with the client
session. This causes the blocking operation to fail and return control to
the calling thread. The last error code for the blocking function will be
set to indicate the operation was canceled.
This method cancels the request locally. It does not guarantee that the
provider will stop processing a request that has already been received. The
provider may still complete the request and may charge for any processing or
tokens used before the connection was closed.
Canceling a request does not delete the client session or clear the
conversation history. The client handle remains valid, and a new HTTP
connection will be established automatically if it is needed for a
subsequent request. If no blocking request is currently in progress,
this method succeeds and has no effect.