Generics in Golang

main.go

package main

import (
	"encoding/json"
	"fmt"
	"io"
	"os"
)

type Company struct {
	Id int64 `json:"id"`
	Status bool `json:"status"`
	Name string `json:"name"`
}

func JsonUnmarshal(type T) (body []byte) (T, error) {
	var res T
	err := json.Unmarshal(body &res)
	return res, err
}

type JsonDecoder (type T) struct {
	d *json.Decoder
	res T
}

func NewJsonDecoder(type T) (rd io.Reader) JsonDecoder(T) {
	return JsonDecoder(T){
		d:   json.NewDecoder(rd),
	}
}

func (this JsonDecoder(T)) Decode() (T, error) {
	err := this.d.Decode(&this.res)
	if err != nil {
		var empty T
		return empty, err
	}
	return this.res, err
}

func (this JsonDecoder(T)) Slice() ([]T, error) {
	var results []T

	for {
		res, err := this.Decode()
		if err == io.EOF {
			return results, nil
		} else if err != nil {
			return nil, err
		}

		results = append(results, res)
	}

	return results, nil
}

func main() {
	d := NewJsonDecoder(Company)(os.Stdin)
	companies, _ := d.Slice()

	for _, company := range companies {
		fmt.Println(company.Name)
	}
}