Gateway NewRequestParser json.NewDecoder map result in loss of numerical precision

[JiekeW]

Describe the bug
Gateway NewRequestParser json.NewDecoder map result in loss of numerical precision

1. The code is

// NewRequestParser creates a new request parser from the given http.Request and resolver.
func NewRequestParser(r *http.Request, resolver jsonpb.AnyResolver) (grpcurl.RequestParser, error) {
	vars := pathvar.Vars(r)
	params, err := httpx.GetFormValues(r)
	if err != nil {
		return nil, err
	}

	for k, v := range vars {
		params[k] = v
	}

	body, ok := getBody(r)
	if !ok {
		return buildJsonRequestParser(params, resolver)
	}

	if len(params) == 0 {
		return grpcurl.NewJSONRequestParser(body, resolver), nil
	}

	m := make(map[string]any)
	if err := json.NewDecoder(body).Decode(&m); err != nil && err != io.EOF {
		return nil, err
	}
	for k, v := range params {
		m[k] = v
	}
	return buildJsonRequestParser(m, resolver)
}

2. The error is
   1975103407695073280 -> 1975103407695073300

3. My solution is

// NewRequestParser creates a new request parser from the given http.Request and resolver.
func NewRequestParser(r *http.Request, resolver jsonpb.AnyResolver) (grpcurl.RequestParser, error) {
	vars := pathvar.Vars(r)
	params, err := httpx.GetFormValues(r)
	if err != nil {
		return nil, err
	}

	for k, v := range vars {
		params[k] = v
	}

	body, ok := getBody(r)
	if !ok {
		return buildJsonRequestParser(params, resolver)
	}

	if len(params) == 0 {
		return grpcurl.NewJSONRequestParser(body, resolver), nil
	}

	m := make(map[string]any)
	decoder := json.NewDecoder(body)
	decoder.UseNumber()
	if err := decoder.Decode(&m); err != nil && err != io.EOF {
		return nil, err
	}
	for k, v := range params {
		m[k] = v
	}
	return buildJsonRequestParser(m, resolver)
}