Why the type of failpoint.Value can't be string

[pingcap]

Why the type of failpoint.Value can't be string

[amyangfei]

ref to: #61

Should use either GO_FAILPOINTS="mypackagename/demoPanic=return(\"100\")" or GO_FAILPOINTS='mypackagename/demoPanic=return("100")'

[jinjiaKarl]

// add.go
func add(ctx context.Context) string {
     failpoint.InjectContext(ctx, "failpoint-name1", func(value failpoint.Value) string {
         failpoint.Return(value.(string))
     })

     return "1"
 }
// add_test.go
 func TestAdd(t *testing.T) {
     err := failpoint.Enable("golangtest/gofailpoint/failpoint-name1", "return('0.01')")
     if err != nil {
         log.Fatal(err)
     }
failpoints := map[string]struct{}{
         "golangtest/gofailpoint/failpoint-name1": {},
     }
     ctx := failpoint.WithHook(context.Background(), func(ctx context.Context, fpname string) bool {
         _, found := failpoints[fpname]
         return found
     })
     log.Println(add(ctx))
 }

when I execute my program, it truns out that:

error on golangtest/gofailpoint/failpoint-name1: failpoint: failed to parse "return('0.01')" past ")"

how come does not it support "return('0.01')" of this pattern?