Sharing values between middleware

<p>Hi all,</p> <p>I am new to Go and would like suggestions on how to share values between middleware.</p> <p>I currently am writing a JSON body parser middleware for my api and don&#39;t really know how to share values to the next handler call. So my code looks something like this:</p> <pre><code>// BodyParser parses incoming JSON requests func BodyParser(val {}interface, next http.Handler, w http.ResponseWriter, req *http.Request) error { type := reflect.TypeOf(val) val := reflect.New(type).Interface() err := json.NewDecoder(r.Body).Decode(val) if (err != nil) { // handle error here } // best way of storing shared middleware value? next.ServeHTTP(w,r) return nil } </code></pre> <p>I was thinking of using Context, but I read some articles that said using context is a bad idea, so I am wondering if there are other ways of doing it without using Context? Any suggestions would be great, thanks!</p> <hr/>**评论：**<br/><br/>TheMerovius: <pre><p>Why do this as a middleware? There seems to be no actual value provided. I&#39;d just use a function</p> <pre><code>func ParseBody(v interface{}, req *http.Request, res http.ResponseWriter) error { if err := json.NewDecoder(r.Body).Decode(v); err != nil { // handle error here } return nil } </code></pre> <p>and call that from a handler.</p></pre>freetoplay123: <pre><p>I didn&#39;t know this was the best way of handling JSON request body in Go. Coming from other languages, they always had a JSON parser middleware. Thanks for the info!</p></pre>joncalhoun: <pre><p>I have mixed feelings about the approach you are taking, but this article may help give you a few ideas - <a href="https://www.calhoun.io/pitfalls-of-context-values-and-how-to-avoid-or-mitigate-them/" rel="nofollow">https://www.calhoun.io/pitfalls-of-context-values-and-how-to-avoid-or-mitigate-them/</a></p> <p>Context values aren&#39;t bad by themselves, and they are pretty useful for middleware, but you just need to use some caution with them and not throw everything under the sun in a context value</p> <p>If you have follow-up questions let me know - I wrote the linked article.</p></pre>freetoplay123: <pre><p>Thanks, this gave me a better understanding of Context.</p></pre>tgulacsi: <pre><p>Use a struct and define the handler as method. This way you can store anything on the struct. But I&#39;d prefer the github.com/go-kit/kit way: have a Decoder which decodes the http request, and returns a nicely filled struct; have an Endpoint which receives that processed struct, does its job, then returns another struct with the data to be returned; then have an Encoder, which outputs as needed from the struct into the ResponseWriter.</p></pre>