Add io.CopyBuffer function to rule G110

Signed-off-by: Cosmin Cojocar <cosmin.cojocar@gmx.ch>

testutils/source.go

@@ -699,12 +699,40 @@ func main() {
 	if err != nil {
 		panic(err)
 	}
-	io.Copy(os.Stdout, r)
+	_, err := io.Copy(os.Stdout, r)
+	if err != nil {
+		panic(err)
+	}
 
 	r.Close()
 }`}, 1, gosec.NewConfig()}, {[]string{`
 package main
 
+import (
+	"bytes"
+	"compress/zlib"
+	"io"
+	"os"
+)
+
+func main() {
+	buff := []byte{120, 156, 202, 72, 205, 201, 201, 215, 81, 40, 207,
+		47, 202, 73, 225, 2, 4, 0, 0, 255, 255, 33, 231, 4, 147}
+	b := bytes.NewReader(buff)
+
+	r, err := zlib.NewReader(b)
+	if err != nil {
+		panic(err)
+	}
+	buf := make([]byte, 8)
+	_, err := io.CopyBuffer(os.Stdout, r, buf)
+	if err != nil {
+		panic(err)
+	}
+	r.Close()
+}`}, 1, gosec.NewConfig()}, {[]string{`
+package main
+
 import (
 	"archive/zip"
 	"io"