kubernetes/staging/src/k8s.io/client-go/tools/portforward/fallback_dialer.go

var _ …

type FallbackDialer …

// NewFallbackDialer creates the FallbackDialer with the primary and secondary dialers,
// as well as the boolean function to determine if the primary dialer failed.
func NewFallbackDialer(primary, secondary httpstream.Dialer, shouldFallback func(error) bool) httpstream.Dialer { … }

// Dial is the single function necessary to implement the "httpstream.Dialer" interface.
// It takes the protocol version strings to request, returning an the upgraded
// httstream.Connection and the negotiated protocol version accepted. If the initial
// primary dialer fails, this function attempts the secondary dialer. Returns an error
// if one occurs.
func (f *FallbackDialer) Dial(protocols ...string) (httpstream.Connection, string, error) { … }