如何在不解析表行的情况下更改结构上的日期格式，例如“ yyyy-mm-dd”？

I would to change EntryDate format like yyyy-mm-dd formated on the struct,

type Value struct {
    Id uint `json:”id”`
    EntryDate time.time `json:”entry_date”`
    ProductId int `json:"product_id"`
    Value float64 `json:”value”`
}

By default the result like this

{
  Id: 11,
  EntryDate: "2017-11-23T00:00:00Z",
  product_id: 1,
  Value: 932.3
},

How to change EntryDate format like "yyyy-mm-dd" on the struct without parsing on the code ?

Change the struct type without parsing at loops ? check this article http://sosedoff.com/2016/07/16/golang-struct-tags.html

If I am understanding you correctly you can do this like this:

package main

import (
    "encoding/json"
    "fmt"
    "time"
)

type Value struct {
    Id        uint      `json:”id”`
    EntryDate time.Time `json:”entry_date”`
    ProductId int       `json:"product_id"`
    Value     float64   `json:”value”`
}

func main() {
    val := Value{}
    val.Id = 1
    val.EntryDate = time.Now().UTC()
    val.ProductId = 2
    val.Value = 1.223
    t := val.EntryDate.UTC().Format("2006-01-02")
    fmt.Println("formated time : ", t)
    b, err := json.Marshal(val)
    if err != nil {
        fmt.Println("failed to marshal object", err)
        return
    }
    fmt.Println("actual object", string(b))
}

Output

 formated time : 2009-11-10
actual object {"Id":1,"EntryDate":"2009-11-10T23:00:00Z","product_id":2,"Value":1.223}

Check in Go playground: https://play.golang.org/p/Fc35ealF5BI