Why does marshalling a json.RawMessage value result in a base64-encoded string instead of raw JSON?

Marshalling json.RawMessage Returns Base64-Encoded String

Question:

When marshalling a json.RawMessage value, why is the output a base64-encoded string instead of the raw JSON?

Background:

The code below demonstrates the issue:

package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    raw := json.RawMessage(`{"foo":"bar"}`)
    j, err := json.Marshal(raw)
    if err != nil {
        panic(err)
    }
    fmt.Println(string(j))  
}

Expected Output:

{"foo":"bar"}

Actual Output:

"eyJmb28iOiJiYXIifQ=="

Answer:

The json.RawMessage type's MarshalJSON method simply returns the underlying byte slice. However, for json.RawMessage to work properly, the value passed to json.Marshal must be a pointer.

Solution:

To fix the issue, update the code as follows:

j, err := json.Marshal(&raw)

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