public String readString(Charset charset) throws IOException {
        return readString(readVarInt(), charset);
    }
Reads binary string from the input stream. {@link #readVarInt()} will be
first called automatically to understand byte length of the string.

@param charset charset, null is treated as {@link StandardCharsets#UTF_8}
@return non-null string
@throws IOException when failed to read value from input stream, not able to
                    retrieve all bytes, or reached end of the stream
clickhouse-data/src/main/java/com/clickhouse/data/ClickHouseInputStream.java