Fix failing test on call to sqlx.In with (driver.Valuer)(nil)

Author: moxar

bind.go

@@ -163,7 +163,7 @@ func In(query string, args ...interface{}) (string, []interface{}, error) {
 	for i, arg := range args {
 		if a, ok := arg.(driver.Valuer); ok {
 			var err error
-			arg, err = a.Value()
+			arg, err = callValuerValue(a)
 			if err != nil {
 				return "", nil, err
 			}
@@ -263,3 +263,24 @@ func appendReflectSlice(args []interface{}, v reflect.Value, vlen int) []interfa
 
 	return args
 }
+
+// callValuerValue returns vr.Value(), with one exception:
+// If vr.Value is an auto-generated method on a pointer type and the
+// pointer is nil, it would panic at runtime in the panicwrap
+// method. Treat it like nil instead.
+// Issue 8415.
+//
+// This is so people can implement driver.Value on value types and
+// still use nil pointers to those types to mean nil/NULL, just like
+// string/*string.
+//
+// This function is copied from database/sql/driver package
+// and mirrored in the database/sql package.
+func callValuerValue(vr driver.Valuer) (v driver.Value, err error) {
+	if rv := reflect.ValueOf(vr); rv.Kind() == reflect.Pointer &&
+		rv.IsNil() &&
+		rv.Type().Elem().Implements(reflect.TypeOf((*driver.Valuer)(nil)).Elem()) {
+		return nil, nil
+	}
+	return vr.Value()
+}