What version of Go are you using (go version)?

go 1.15.6

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

1. GOOS="darwin", GOARCH="amd64"
2. GOOS="linux", GOARCH="amd64"

What did you do?

func TestCookieParse(t *testing.T) {
	req, err := http.NewRequest(http.MethodGet, "http://localhost", nil)
	if err != nil {
		t.Error(err)
		return
	}

	req.Header = http.Header{
		"Cookie": []string{"name=1;;age=2"},
	}

	if c, err := req.Cookie("age"); err != nil {
		t.Error(err)
		return
	} else if c.Value != "2" {
		t.Errorf("age have: %s, want: 2", c.Value)
		return
	}
}

What did you expect to see?

The test passes as expected, and the value of "age" should be "2".

What did you see instead?

The test failed with an error as "http: named cookie not present".

My View

I parsed the same cookie string in PHP and NodeJS, and both of them return the value of "age" as "2".

And I tried the same code in Go 1.12, the value of "age" is also "2".

Is this a bug since Go 1.13 or just a feature ?

If this is a bug, you can fix it just like the below code:

old code in net/http/cookie.go:250

if splitIndex := strings.Index(line, ";"); splitIndex > 0 {

new code

if splitIndex := strings.Index(line, ";"); splitIndex >= 0 {