Hi.

Consider this code:

package main

import (
    "fmt"
)

type bug struct {
    a int
    b int `js:"b"`
}

func main() {
    v := bug{a: 10, b: 10}
    fmt.Println(v)
}

When I run it I get an error:
Error: reflect: call of ?FIXME? on int Value

In order to reproduce this problem, it is necessary to have two fields, of any type.
The error message will report the type of the first field (int in the example).