读取可接受数据中的特定字节数

I have a binary package of data, but length of the package is a first 4 bytes of it. Is there a correct way to read length and then read whole package with net.Conn in GoLang?

Try using this:

package main

import ( "encoding/binary" "io" )

func ReadPacket(r io.Reader) ([]byte, error) {
    lenB := make([]byte, 4)

    if _, err := r.Read(lenB); err != nil {
        return nil, err
    }

    //you can use BigEndian depending on the proto
    l := binary.LittleEndian.Uint32(lenB)

    packet := make([]byte, l)

    _, err := r.Read(packet)

    return packet, err
}