REST端在1.6之后的go版本中返回404

Question

I upgraded from 1.6 golang to 1.9 (and 1.10) and all REST calls are now returning 404. They were working fine with 1.6.

main.go

import ( "net/http" )

func main() {
   mux := http.NewServeMux()
   handlers.TableHandler(*mux)
}

table_handler.go

func TableHandler(mux http.ServeMux) {
    mux.HandleFunc("/gpdp/v1/prices/", func(w http.ResponseWriter, r *http.Request) 

        log.Println("request for prices: ", r.Method, r.Body)
...}

Answer 1

The main function copies the mux value when calling the TableHandler function. The TableHandler function modifies the copy. This value is discarded on return from the TableHandler function. The result is the handler is not registered in main()'s mux.

The fix is to change the TableHandler argument type from http.ServeMux to *http.ServeMux.

import ( "net/http" )

func main() {
   mux := http.NewServeMux()
   handlers.TableHandler(mux)  // <--- pass pointer here
}

func TableHandler(mux *http.ServeMux) {  // <--- declare arg as pointer
    mux.HandleFunc("/gpdp/v1/prices/", func(w http.ResponseWriter, r *http.Request) 

        log.Println("request for prices: ", r.Method, r.Body)
...}

The application stopped working because of a change to http.ServeMux in 2016. This change exposed the problem in the application. Copying http.ServeMux values was never supported. The go vet command prints a warning when http.ServeMux values are copied.