package main import ( "fmt" "net/http" "strings" ) func jsonHeaderMiddleware(next http.Handler) http.Handler { return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { fmt.Println(r.URL.Path) if strings.HasPrefix(r.URL.Path, "/api/") { w.Header().Add("Content-Type", "application/json") } next.ServeHTTP(w, r) }) }