server.go
func (ctx *RequestCtx) SetUserValueBytes(key []byte, value interface{}) {
	ctx.userValues.SetBytes(key, value)
}
func (ctx *RequestCtx) SetUserValueBytes(key []byte, value interface{}) {
	ctx.userValues.SetBytes(key, value)
}
// SetUserValueBytes stores the given value (arbitrary object)
// under the given key in ctx.
//
// The value stored in ctx may be obtained by UserValue*.
//
// This functionality may be useful for passing arbitrary values between
// functions involved in request processing.
//
// All the values stored in ctx are deleted after returning from RequestHandler.