var s string
str := "123"
str += "123123"
str += "qwerqwe"
var s string = "12312sf"
s = fmt.Sprintf("%s %s",s,"123123")
s := "1231"
strings.Join([]string{s,"ewrwer"},"")
var s []string
s = append(s,"123123")
strings.Join(s,"")
var buf bytes.Buffer
buf.WriteString("12312")
buf.WriteString("werwer")
buf.String()
WriteString()参数一定是string,不能是byte
b.WriteString(string(s[len(s)-1-i]))
b.WriteString(s[len(s)-1-i,len(s)-i])