when fields greater than ten,unmarshal fails

[songhaitao]

type S1 struct {
	A string
	B string
	C string
}

type S2 struct {
	A string
	B string
	C string
	D string
	E string
	F string
	G string
	H string
	I string
	J string
	K string
}

func main() {
	var json = jsoniter.ConfigCompatibleWithStandardLibrary
	s1str := `{"a":"1","b":"2","c":"3"}`
	s1 := &S1{}
	json.UnmarshalFromString(s1str, s1)
	fmt.Printf("%+v\n", s1)

	s2str := `{"a":"1","b":"2","c":"3","d":"4","e":"5","f":"6","g":"7","h":"8","i":"9","j":"10","k":"11"}`
	s2 := &S2{}
	json.UnmarshalFromString(s2str, s2)
	fmt.Printf("%+v\n", s2)
}

运行结果:
&{A:1 B:2 C:3}
&{A: B: C: D: E: F: G: H: I: J: K:}

json库版本:1.1.3

虽然可以通过设置属性的TAG来解决，但是感觉解码行为受结构体属性个数影响导致行为不一致有点小坑，所以提出这个ISSUE。

go/reflect_struct_decoder.go

Line 515 in ca39e5a

fieldDecoder = decoder.fields[strings.ToLower(field)]

其实这里也尝试了转小写去寻找fieldDecoder，只是场景可能有点多。