Replace go1.17 unsafe.Slice with go1.16 compatible code.

Author: tunabay

go.mod

@@ -1,5 +1,5 @@
 module github.com/tunabay/go-bitarray
 
-go 1.17
+go 1.16
 
 require gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b

util.go

@@ -6,6 +6,7 @@ package bitarray
 
 import (
 	"fmt"
+	"reflect"
 	"unsafe"
 )
 
@@ -345,14 +346,14 @@ func allocByteSlice(nBytes int) []byte {
 func asUint64Slice(b []byte) []uint64 {
 	// s := (*[cap(b)>>3]uint64)(unsafe.Pointer(&b[0]))[:]
 
-	// n := (len(b) + 7) >> 3
-	// s := make([]uint64, 0)
-	// h := (*reflect.SliceHeader)(unsafe.Pointer(&s))
-	// h.Data, h.Len, h.Cap = uintptr(unsafe.Pointer(&b[0])), n, n
+	n := (len(b) + 7) >> 3
+	s := make([]uint64, 0)
+	h := (*reflect.SliceHeader)(unsafe.Pointer(&s))
+	h.Data, h.Len, h.Cap = uintptr(unsafe.Pointer(&b[0])), n, n
 
 	// Since go1.17
-	//nolint:typecheck // 2021-08-21: v1.42.0 does not support go1.17?
-	s := unsafe.Slice((*uint64)(unsafe.Pointer(&b[0])), (len(b)+7)>>3)
+	// 2021-08-21: golangcilint v1.42.0 does not support go1.17?
+	// s := unsafe.Slice((*uint64)(unsafe.Pointer(&b[0])), (len(b)+7)>>3)
 
 	return s
 }