net/http: Pattern matching of ServeMux works weird and unexpected

[junchih]

Go version

go version go1.23.3 darwin/amd64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='darwin'
GOINSECURE=''
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/Cellar/go/1.23.3/libexec'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='local'
GOTOOLDIR='/usr/local/Cellar/go/1.23.3/libexec/pkg/tool/darwin_amd64'
GOVCS=''
GOVERSION='go1.23.3'
GODEBUG=''
GOTELEMETRY='local'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='cc'
CXX='c++'
CGO_ENABLED='1'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/n5/tfyr71j10156jfb_hjg81vt80000gn/T/go-build3817963952=/tmp/go-build -gno-record-gcc-switches -fno-common'

What did you do?

With the blow code running, go with curl -X GET --verbose 127.0.0.1:8080/ping0 and curl -X GET --verbose 127.0.0.1:8080/ping1

package main

import (
	"net/http"
)

func main() {
	handler := http.NewServeMux()
	handler.HandleFunc("GET /ping0", func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
	})
	handler.HandleFunc("/ping1", func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
	})
	server := &http.Server{
		Addr:    ":8080",
		Handler: handler,
	}
	server.ListenAndServe()
}

What did you see happen?

$ curl -X GET --verbose 127.0.0.1:8080/ping0
Note: Unnecessary use of -X or --request, GET is already inferred.
*   Trying 127.0.0.1:8080...
* Connected to 127.0.0.1 (127.0.0.1) port 8080
> GET /ping0 HTTP/1.1
> Host: 127.0.0.1:8080
> User-Agent: curl/8.7.1
> Accept: */*
>
* Request completely sent off
< HTTP/1.1 404 Not Found
< Content-Type: text/plain; charset=utf-8
< X-Content-Type-Options: nosniff
< Date: Wed, 13 Nov 2024 04:42:42 GMT
< Content-Length: 19
<
404 page not found
* Connection #0 to host 127.0.0.1 left intact

$ curl -X GET --verbose 127.0.0.1:8080/ping1
Note: Unnecessary use of -X or --request, GET is already inferred.
*   Trying 127.0.0.1:8080...
* Connected to 127.0.0.1 (127.0.0.1) port 8080
> GET /ping1 HTTP/1.1
> Host: 127.0.0.1:8080
> User-Agent: curl/8.7.1
> Accept: */*
>
* Request completely sent off
< HTTP/1.1 200 OK
< Date: Wed, 13 Nov 2024 04:42:44 GMT
< Content-Length: 0
<
* Connection #0 to host 127.0.0.1 left intact

What did you expect to see?

Two curl commands above, work the same.

[gabyhelp]

Related Issues

• net/http: ServeMux behaves inconsistently across operating systems #66288 (closed)
• net/http: Conflicts with pattern when using NewServeMux #68838 (closed)
• net/http: enhanced ServerMux routing #65231 (closed)
• net/http: 301 instead of 404 for unmatched requests #65624 (closed)
• x/website, x/pkgsite: net/http.ServeMux.Handle example reads poorly if shown as a complete program #40103
• net/http: ServeMux.Handler does not populate named path wildcards #69623
• net/http: document and test behavior of ServeMux with ports #23351 (closed)
• net/http: muxer no longer redirects host patterns in go1.10 #23183 (closed)
• net/http: ServeMux not validating methods for redirected paths #69690 (closed)
• net/http: ServeMux forcibly cleans double forward slash in URLs even when behaving as a gateway #42244 (closed)

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