Bug report criteria

• This bug report is not security related, security issues should be disclosed privately via security@etcd.io.
• This is not a support request, support requests should be raised in the etcd discussion forums.
• You have read the etcd bug reporting guidelines.
• Existing open issues along with etcd frequently asked questions have been checked and this is not a duplicate.

What happened?

Test function UniqueURLsFromFlag:

func TestUniqueURLsFromFlag(t *testing.T) {
	const name = "test"
	urls := []string{
		"https://1.2.3.4:1",
		"https://1.2.3.4:2",
		"https://1.2.3.4:3",
		"https://1.2.3.4:1",
	}
	fs := flag.NewFlagSet(name, flag.ExitOnError)
	u := NewUniqueURLsWithExceptions(strings.Join(urls, ","))
	fs.Var(u, name, "usage")
	uss := UniqueURLsFromFlag(fs, name)

	require.Equal(t, len(u.Values), len(uss))

	um := make(map[string]struct{})
	for _, x := range uss {
		um[x.String()] = struct{}{}
	}
	require.Equal(t, u.Values, um)
}

Error Trace:    /Users/jes/go/src/etcd/pkg/flags/unique_urls_test.go:113
                Error:          Not equal:
                                expected: 3
                                actual  : 4
                Test:           TestUniqueURLsFromFlag

What did you expect to happen?

None

How can we reproduce it (as minimally and precisely as possible)?

Run the test.

Anything else we need to know?

No response

Etcd version (please run commands below)

Sorry, I only reviewed the code and tested it.
No more details could be provided.

Etcd configuration (command line flags or environment variables)

No response

Etcd debug information (please run commands below, feel free to obfuscate the IP address or FQDN in the output)

No response

Relevant log output

No response