You could use net/context with http.Handler. for example you have "X-Request-ID" in header, you could define middlware like this:
func middleware(next http.Handler) http.Handler {
return http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
ctx := newContextWithRequestID(req.Context(), req)
next.ServeHTTP(rw, req.WithContext(ctx))
})
}
type key int
const requestIDKey key = 0
func newContextWithRequestID(ctx context.Context, req *http.Request) context.Context {
reqID := req.Header.Get("X-Request-ID")
if reqID == "" {
reqID = generateRandomID()
}
return context.WithValue(ctx, requestIDKey, reqID)
}
func requestIDFromContext(ctx context.Context) string {
return ctx.Value(requestIDKey).(string)
}
you could get requestIDKey in any handler with Context object.
func handler(rw http.ResponseWriter, req *http.Request) {
reqID := requestIDFromContext(req.Context())
fmt.Fprintf(rw, "Hello request ID %v
", reqID)
}
this is just an example. insted of requestIDKey you could have any data which you should put in Context and read from it with a key.
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