go fmt with go 1.17

The build tags have changed... I am highly sceptical of what this means for older go versions whose tests will likely now fail.

But as these are build tags, I cannot see how I can avoid updating them to the newer format.

This is the way for the future... if it breaks the past then hmmmm.

sanitize_go1.8_test.go

@@ -27,6 +27,7 @@
 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+//go:build go1.8
 // +build go1.8
 
 package bluemonday

sanitize_ltgo1.8_test.go

@@ -27,6 +27,7 @@
 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+//go:build go1.1 && !go1.8
 // +build go1.1,!go1.8
 
 package bluemonday

stringwriterwriter_go1.12.go

@@ -1,3 +1,4 @@
+//go:build go1.12
 // +build go1.12
 
 package bluemonday

stringwriterwriter_ltgo1.12.go

@@ -1,3 +1,4 @@
+//go:build go1.1 && !go1.12
 // +build go1.1,!go1.12
 
 package bluemonday