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🔄 Convert CSV to JSON in Go

·2 mins
Introduction File Csv Json

To convert CSV data to JSON in Go, you should follow these steps:

  1. Create a struct for storing CSV lines and annotate it with JSON struct field tags.
  2. Read CSV file using csv.Reader.
  3. Assign successive lines of raw CSV data to instances of the created struct.
  4. Convert an array of structs to JSON using marshaling functions from the encoding/json package.

In the example below, we use data.csv file:

vegetables,fruits,rank
carrot,banana,1
potato,strawberry,2

See also our examples of how to convert JSON to CSV and how to read CSV file or how to write data to a CSV file in Go

package main

import (
    "encoding/csv"
    "encoding/json"
    "fmt"
    "log"
    "os"
    "strconv"
)

type ShoppingRecord struct {
    // 1. Create a struct for storing CSV lines and annotate it with JSON struct field tags
    Vegetable string `json:"vegetable"`
    Fruit     string `json:"fruit"`
    Rank      int    `json:"rank"`
}

func createShoppingList(data [][]string) []ShoppingRecord {
    // convert csv lines to array of structs
    var shoppingList []ShoppingRecord
    for i, line := range data {
        if i > 0 { // omit header line
            var rec ShoppingRecord
            for j, field := range line {
                if j == 0 {
                    rec.Vegetable = field
                } else if j == 1 {
                    rec.Fruit = field
                } else if j == 2 {
                    var err error
                    rec.Rank, err = strconv.Atoi(field)
                    if err != nil {
                        continue
                    }
                }
            }
            shoppingList = append(shoppingList, rec)
        }
    }
    return shoppingList
}

func main() {
    // open file
    f, err := os.Open("data.csv")
    if err != nil {
        log.Fatal(err)
    }

    // remember to close the file at the end of the program
    defer f.Close()

    // 2. Read CSV file using csv.Reader
    csvReader := csv.NewReader(f)
    data, err := csvReader.ReadAll()
    if err != nil {
        log.Fatal(err)
    }

    // 3. Assign successive lines of raw CSV data to fields of the created structs
    shoppingList := createShoppingList(data)

    // 4. Convert an array of structs to JSON using marshaling functions from the encoding/json package
    jsonData, err := json.MarshalIndent(shoppingList, "", "  ")
    if err != nil {
        log.Fatal(err)
    }

    fmt.Println(string(jsonData))
}

Output:

[
  {
    "vegetable": "carrot",
    "fruit": "banana",
    "rank": 1
  },
  {
    "vegetable": "potato",
    "fruit": "strawberry",
    "rank": 2
  }
]