add "endpointsFunc" in the struct ginNobl

[peacess]

in old version "github.com/improbable-eng/grpc-web", it can not modify the "endpointsFunc", so we do follow:

if len(c.preUrl) > 0 { // because can not set the "endpointFunc" of WrapServer, do this so so
old := ctx.Request.URL.Path
if strings.HasPrefix(old, c.preUrl) {
index := len(c.preUrl) - 1
ctx.Request.URL.Path = old[index:]
}
}
but in new version, can modiry the "endpointsFunc", it will be better to replace with "endpointsFunc"