String Internals

Fill in the blank in line A, to convert b from []byte to string without causing memory copy.The expected output is "143"

package main
import (
    "fmt"
    "unsafe"
)
func main() {
    var b = []byte("123")
    s := __ //A
    b[1] = '4'
    fmt.Printf("%+v\n", s) //print 143
}

Answer

package main
import (
    "fmt"
    "unsafe"
)
func main() {
    var b = []byte("123")
    s := *(*string)(unsafe.Pointer(&b))
    b[1] = '4'
    fmt.Printf("%+v\n", s) //print 143
}