In your sample code data should be JSON-encoded (in simple word String) so you are using Unmarshal in a wrong way:

// Unmarshal parses the JSON-encoded data and stores the result
// in the value pointed to by v. If v is nil or not a pointer,
// Unmarshal returns an InvalidUnmarshalError.
func Unmarshal(data []byte, v interface{}) error

Try it on The Go Playground and this: []string{"art", "football"}:

package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    // ********************* Marshal *********************
    u := map[string]interface{}{}
    u["name"] = "kish"
    u["age"] = 28
    u["work"] = "engine"
    //u["hobbies"] = []string{"art", "football"}
    u["hobbies"] = "art"

    b, err := json.Marshal(u)
    if err != nil {
        panic(err)
    }
    fmt.Println(string(b))

    // ********************* Unmarshal *********************
    var a interface{}
    err = json.Unmarshal(b, &a)
    if err != nil {
        fmt.Println("error:", err)
    }
    fmt.Println(a)
}

output:

{"age":28,"hobbies":"art","name":"kish","work":"engine"}
map[name:kish work:engine age:28 hobbies:art]

You want to Unmarshal it, so try this simple working example ([]byte(kpi.(string))):

package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    var kpi interface{} = st
    var a []Animal
    err := json.Unmarshal([]byte(kpi.(string)), &a)
    if err != nil {
        fmt.Println("error:", err)
    }
    fmt.Println(a)
}

type Animal struct {
    Name  string
    Order string
}

var st = `[
    {"Name": "Platypus", "Order": "Monotremata"},
    {"Name": "Quoll",    "Order": "Dasyuromorphia"}
]`

output:

[{Platypus Monotremata} {Quoll Dasyuromorphia}]

Working example using ([]byte(*kpi.(*string))):

package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    var kpi interface{} = &st
    var a []Animal
    err := json.Unmarshal([]byte(*kpi.(*string)), &a)
    if err != nil {
        fmt.Println("error:", err)
    }
    fmt.Println(a)
}

type Animal struct {
    Name  string
    Order string
}

var st = `[
    {"Name": "Platypus", "Order": "Monotremata"},
    {"Name": "Quoll",    "Order": "Dasyuromorphia"}
]`

Marshal:

package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    u := map[string]interface{}{}
    u["1"] = "one"
    b, err := json.Marshal(u)
    if err != nil {
        panic(err)
    }
    fmt.Println(string(b))
}

output:

{"1":"one"}

I hope this helps.

When you unmarshall JSON into interface{}, it has no way to know what type you want it to use, so it defaults to map[string]interface{} as indicated in the documentation:

To unmarshal JSON into an interface value, Unmarshal stores one of these in the interface value:

...

map[string]interface{}, for JSON objects

If you want to unmarshal to a specific type, pass an instance of that type to Unmarshal:

var result sample 
err = json.Unmarshal(data,&result)

Other problems in my code led me away from the gob package earlier, turns out it was the proper way as @nvcnvn suggested. Relevant code on how to solve this issue below:

package bloom

import (
    "encoding/gob"
    "bytes"
)

func GetBytes(key interface{}) ([]byte, error) {
    var buf bytes.Buffer
    enc := gob.NewEncoder(&buf)
    err := enc.Encode(key)
    if err != nil {
        return nil, err
    }
    return buf.Bytes(), nil
}

You can use a Short variable declaration in the Type switch to have the typed value in the case branches:

switch v := any.(type) {
case bytes.Buffer: // return as is
    return v.String() // Here v is of type bytes.Buffer
}

Try it on the Go Playground.

Quoting form the spec:

The TypeSwitchGuard may include a short variable declaration. When that form is used, the variable is declared at the beginning of the implicit block in each clause. In clauses with a case listing exactly one type, the variable has that type; otherwise, the variable has the type of the expression in the TypeSwitchGuard.