Listing 9.11: traceid middleware

June 24, 2025 · View on GitHub

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link / kit / traceid / http.go

package traceid

import "net/http"

// Middleware adds a new trace ID to [http.Request.Context].
func Middleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if _, ok := FromContext(r.Context()); !ok {
			ctx := WithContext(r.Context(), New())
			r = r.WithContext(ctx)
		}
		next.ServeHTTP(w, r)
	})
}