Trie is broken

[zhulik]

func TestKeys(t *testing.T) {
	tr := trie.New[int]()
	tr.Put("topic1", 1)
	tr.Put("topic2", 2)
	assert.Equal(t, []string{"topic1", "topic2"}, tr.Keys())
}

The result is

--- FAIL: TestKeys (0.00s)
    trie_test.go:68: 
                Error Trace:    trie_test.go:68
                Error:          Not equal: 
                                expected: []string{"topic1", "topic2"}
                                actual  : []string{"topic1", "topi2"}
                            
                                Diff:
                                --- Expected
                                +++ Actual
                                @@ -2,3 +2,3 @@
                                  (string) (len=6) "topic1",
                                - (string) (len=6) "topic2"
                                + (string) (len=5) "topi2"
                                 }
                Test:           TestKeys
FAIL
exit status 1
FAIL    github.com/zhulik/go-eventbus/trie      0.004s