sm3 does not correctly implement hash.Hash

[cloudwindy]

gmsm/sm3/sm3.go

Lines 229 to 251 in 36b992c

	// 返回SM3哈希算法摘要值
	// Sum appends the current hash to b and returns the resulting slice.
	// It does not change the underlying hash state.
	func (sm3 *SM3) Sum(in []byte) []byte {
	_, _ = sm3.Write(in)
	msg := sm3.pad()
	//Finalize
	digest := sm3.update2(msg)
	// save hash to in
	needed := sm3.Size()
	if cap(in)-len(in) < needed {
	newIn := make([]byte, len(in), len(in)+needed)
	copy(newIn, in)
	in = newIn
	}
	out := in[len(in) : len(in)+needed]
	for i := 0; i < 8; i++ {
	binary.BigEndian.PutUint32(out[i*4:], digest[i])
	}
	return out
	}

It should append the current hash to the slice, instead of treating it as an input.