Fix macOS breakage

define.go

@@ -5,7 +5,10 @@ package goclamav
 #include <stdlib.h>
 */
 import "C"
-import "errors"
+import (
+	"errors"
+	"fmt"
+)
 
 // ErrorCode models ClamAV errors
 type ErrorCode C.cl_error_t
@@ -125,7 +128,7 @@ const CL_INIT_DEFAULT C.uint = C.CL_INIT_DEFAULT
 
 // Wraps the corresponding error message
 func Strerr(code ErrorCode) error {
-	err := errors.New(C.GoString(C.cl_strerror(C.int(code))))
+	err := errors.New(fmt.Sprintf("Error %s", C.int(code)))
 	return err
 }