MarshalTo doesn't actually append to the passed in slice about fastjson HOT 5 OPEN

// The out slice is defined once and re-used multiple times
// inside the loop for marshaling different values.
var out []byte
for {
    // obtain v here
    out = v.MarshalTo(out[:0])
    // use out here
}

out := make([]byte, 0, 50000)
outNew := v.MarshalTo(out)
// Verify whether MarshalTo added data to out or put it to another memory
outExtended := out[:len(outNew)]
if bytes.Equal(outNew, outExtended) {
  log.Println("outNew points to out memory")
} else {
  log.Println("outNew points to another memory")
}