panic with JSON in go

Question

I tried to run the following code

package main

import (
    "encoding/json"
    "fmt"
    /*"labix.org/v2/mgo"
    "labix.org/v2/mgo/bson"*/
)

func insertEntry(j *map[string]interface{}, entry string) {
    err := json.Unmarshal([]byte(entry), j)
    if err != nil {
        panic(err)
    }

}

func main() {
    c1 := "{" +
        `"mw" : 42.0922,` +
        `"ΔfH°gas" : {` +
        `   "value" : 372.38,` +
        `   "units" : "kJ/mol"` +
        `},` +
        `"S°gas" : {` +
        `   "value" : 216.81,` +
        `   "units" : "J/mol×K"` +
        `},` +
        `"index" : [` +
        `   {"name" : "mw", "value" : 42.0922},` +
        `   {"name" : "ΔfH°gas", "value" : 372.38},` +
        `   {"name" : "S°gas", "value" : 216.81}` +
        `]` +
        `}`

    c2 := "{" +
        `"name" : "silicon",` +
        `"mw" : 32.1173,` +
        `}` +
        `"index" : [` +
        `   {"name" : "mw", "value" : 32.1173}` +
        `]` +
        `}`

    var m map[string]interface{}

    insertEntry(&m, c1)
    insertEntry(&m, c2)
    chemical := m["ΔfH°gas"].(map[string]interface{})
    fmt.Println("value: %s\n", chemical["value"].(string))
    fmt.Println("units: %s\n", chemical["units"].(string))

But I got the following error message:

    $ go run chemeo.go 
    panic: invalid character '}' looking for beginning of object key string

    goroutine 1 [running]:
    main.insertEntry(0xf840045100, 0x4badc4, 0x7f5e00000056, 0x20043115c)
            /media/mictadlo/projects/mgo/chemeo/chemeo.go:19 +0xd8
    main.main()
            /media/mictadlo/projects/mgo/chemeo/chemeo.go:54 +0xa3

    goroutine 2 [syscall]:
    created by runtime.main
            /usr/local/go/src/pkg/runtime/proc.c:221
    exit status 2

What did I do wrong?

Answer 1

Your c2 variable is holding invalid JSON:

c2 := "{" +
`"name" : "silicon",` +
`"mw" : 32.1173,` +
`}` +
`"index" : [` +
` {"name" : "mw", "value" : 32.1173}` +
`]` +
`}`

Cleaned up, it'll look like this:

c2 := `{
    "name" : "silicon",
    "mw" : 32.1173,
}
"index" : [
    {"name" : "mw", "value" : 32.1173}
]
}`

You can see there's an extra } in the middle.

It should look like this:

c2 := `{
    "name": "silicon",
    "mw": 32.1173,
    "index": [
        {
            "name": "mw",
            "value": 32.1173
        }
    ]
}`