gin-gonic json conversion output throws empty array - go

Question

for the following golang program, i'm not able to get json output using gin-gonic library, if i do fmt.Print variable shows values, but when i convert to c.JSON (inventory) out it shows empty array, what is wrong with my code?
package main
import (
"database/sql"
"os"
"github.com/gin-gonic/gin"
_ "github.com/go-sql-driver/mysql"
)
func index(c *gin.Context) {
hostname, err := os.Hostname()
checkErr(err)
c.String(200, "v3 "+hostname)
}
func healthz(c *gin.Context) {
c.String(200, "OK")
}
type InventoryItem struct {
id int
productID string
productCost int
productAvailabilty int
productSubcat string
}
func checkErr(err error) {
if err != nil {
panic(err)
}
}
/******************* MAIN Function **************/
func main() {
app := gin.Default()
app.GET("/", index)
app.GET("/healthz", healthz)
app.GET("/inventory", fetch)
app.Run(":8000")
}
/******************* End MAIN Function **************/
func fetch(c *gin.Context) {
var (
invt InventoryItem
inventory []InventoryItem
)
connStr := os.Getenv("sql_user") + ":" + os.Getenv("sql_password") + "#tcp(" + os.Getenv("sql_host") + ":3306)/" + os.Getenv("sql_db")
db, err := sql.Open("mysql", connStr)
checkErr(err)
defer db.Close()
rows, err := db.Query("SELECT id,product_id as productID,product_cost as productCost,product_availabilty as productAvailabilty,product_subcat as productSubcat FROM inventory;")
for rows.Next() {
err = rows.Scan(&invt.id, &invt.productID, &invt.productCost, &invt.productAvailabilty, &invt.productSubcat)
checkErr(err)
inventory = append(inventory, invt)
}
checkErr(err)
defer rows.Close()
//fmt.Print(inventory[0].productAvailabilty)
c.JSON(200, inventory)
}

Answer 1

Issue is InventoryItem struct fields have to be exported -
type InventoryItem struct {
ID int `json:"id"`
ProductID string `json:"product_id"`
ProductCost int `json:"product_cost"`
ProductAvailabilty int `json:"product_availability"`
ProductSubcat string `json:"product_subact"`
}
Read more about exported and un-exported fields.