context.go

// WithUUID returns a new Context that carries a uuid. If the UUID
// already exists, nothing is done. Otherwise a new one is created.
func WithUUID(c context.Context) (context.Context, string) {
	if u, ok := c.Value("request.id").(string); ok {
		return c, u
	}

	uuid := uuid.New()
	return context.WithValue(c, "request.id", uuid), uuid
}

// FromRequest retrieves or creates a UUID from the request and
// accordingly sets the request.id of context.
func FromRequest(c context.Context, req *http.Request) context.Context {
	headers := req.Header.Get("Request-Id")
	if headers != "" {
		return context.WithValue(c, "request.id", headers)
	}
	c, _ = WithUUID(c)
	return c
}

// WithLog retrieves or create a UUID for the context and sets
// a field for it in the log entry.
func WithLog(c context.Context, ll *log.Entry) *log.Entry {
	_, uuid := WithUUID(c)
	return ll.WithFields(log.Fields{"request.id": uuid})
}