Golang HTTP和文件缓存

I have an application, written in Go, which runs an HTTP server and uses http.ServeFile() to serve a file which is being updated 3 times per second; this is an audio streaming index file for a HTTP Live Stream which I need to operate in near zero latency, hence the frequent updates. I can see from the logging in my Go server application that this file really is being updated 3 times per second and I call Sync() on the file each time it is updated to make sure that it is written to disk.

My problem is that, on the browser side (Chrome), while this file is being requested several times per second, it is only actually being served once a second; on all the other occasions the server is returning 304, indicating that the file is unchanged:

What might be causing this behaviour and how could I make the file be served on each request?

As state in the comments, it turns out that the modification time checking in HTTP has a minimum resolution of 1 second and so, where a file needs to be change and server more frequently than that, it's best to serve it oneself from RAM. For instance, store it in a slice called content and serve that slice with something like:

http.ServeContent(w, r, filepath.Base(r.URL.Path), time.Time{}, bytes.NewReader(content))

Modification time checking in HTTP only has resolution to the second. However, the alternative is to use entity-tags ('etags'), which can be updated as often as the server needs to change the content.

Therefore your use-case would work better via etags instead of modification times. An etag contains an opaque string that either does or doesn't match.

From https://tools.ietf.org/html/rfc7232#section-2.3,

An entity-tag is an opaque validator for differentiating between multiple representations of the same resource, regardless of whether those multiple representations are due to resource state changes over time, content negotiation resulting in multiple representations being valid at the same time, or both.

Detection of change by the client is usually done using the if-none-match header (https://tools.ietf.org/html/rfc7232#section-3.2)

If-None-Match is primarily used in conditional GET requests to enable efficient updates of cached information with a minimum amount of transaction overhead.