Read UTF-8 encoded string from io.Reader

Question

I am writing an small communication protocol with TCP sockets. I am able to read and write basic data types such as integers but I have no idea of how to read an UTF-8 encoded string from a slice of bytes.

The protocol client is written in Java and the server is Go.

As per I read: GO runes are 32 bit long and UTF-8 chars are 1 to 4 byte long, what makes not possible to simply cast a byte slice to a String.

I'd like to know how can I read and write this UTF-8 stream.

Note I have the byte buffer length on time to read the string.