为什么Go将字节添加到我的字符串中？

Question

When I add a single byte to my string at 0x80 or above, golang will add 0xc2 before my byte. I think this has something to do with utf8 runes. Either way, how do I just add 0x80 to the end of my string?

Example:

var s string = ""
len(s) // this will be 0
s += string(0x80)
len(s) // this will be 2, string is now bytes 0xc2 0x80

Answer 1

The From the specification:

Converting a signed or unsigned integer value to a string type yields a string containing the UTF-8 representation of the integer.

The expression string(0x80) evaluates to a string with the UTF-8 representation of 0x80, not a string containing the single byte 0x80. The UTF-8 representation of 0x80 is 0xc2 0x80.

Use the \x hex escape to specify the byte 0x80 in a string:

 s += "\x80"

You can create a string from an arbitrary sequence of bytes using the string([]byte) conversion.

 s += string([]byte{0x80})