tocsv

tocsv - Universal CSV Export Library for Go

A library for exporting any data to CSV with full customization options

Quick Start

Installation

go get github.com/go-data-exporter/tocsv

Basic Usage

From SQL Results

package main

import (
	"database/sql"
	"log"
	"os"

	"github.com/go-data-exporter/tocsv"
)

func main() {
	var (
		driver = "pgx"
		dsn    = "postgres://"
	)
	db, err := sql.Open(driver, dsn)
	if err != nil {
		log.Fatalln(err)
	}
	defer db.Close()
	rows, err := db.Query("SELECT id, name, email FROM users")
	if err != nil {
		log.Fatalln(err)
	}
	defer rows.Close()

	writer := tocsv.New(tocsv.NewSQLRowsScanner(rows, driver))
	writer.Write(os.Stdout)
}

From Slice Data

package main

import (
	"os"

	"github.com/go-data-exporter/tocsv"
)

func main() {
	data := [][]any{
		{1, "John Doe", "john@example.com"},
		{2, "Jane Smith", "jane@example.com"},
	}
	rows := tocsv.NewSliceRowsScanner(data)
	writer := tocsv.New(rows)
	writer.Write(os.Stdout)
}

From any other data source

You could create your own implementation of tocsv.RowsScanner interface.

type RowsScanner interface {
	// Next prepares the next result row for reading.
	// Returns true on success, false if no more rows are available.
	Next() bool

	// Scan copies the current row's values into the provided destinations.
	// Each destination must be a pointer to an any value (*any).
	Scan(dest ...any) error

	// Columns returns the column metadata for the current result set.
	Columns() ([]Column, error)

	// Driver returns an identifier for the data source driver.
	Driver() string

	// Err returns any error that occurred during iteration.
	Err() error
}

Advanced Customization

Custom Type Handling

package main

import (
	"os"

	"github.com/go-data-exporter/tocsv"
)

type User struct {
	Firstname string
	Lastname  string
}

func main() {
	data := [][]any{
		{1, User{"User", "1"}},
		{2, User{"User", "2"}},
		{3, User{"User", "3"}},
	}
	writer := tocsv.New(tocsv.NewSliceRowsScanner(data),
		tocsv.WithCustomType(func(u User, _ string, _ tocsv.Column) string {
			return u.Firstname + " " + u.Lastname
		}),
	)
	writer.Write(os.Stdout)
}

Row Processing Callback

package main

import (
	"os"
	"strings"

	"github.com/go-data-exporter/tocsv"
)

type User struct {
	Firstname string
	Lastname  string
}

func main() {
	data := [][]any{
		{1, User{"user", "1"}},
		{2, User{"user", "2"}},
		{3, User{"user", "3"}},
	}
	writer := tocsv.New(tocsv.NewSliceRowsScanner(data),
		tocsv.WithCustomType(func(u User, _ string, _ tocsv.Column) string {
			return u.Firstname + " " + u.Lastname
		}),
		tocsv.WithCallback(func(row []string) ([]string, bool) {
			// Skip "user 2"
			if row[1] == "user 2" {
				return nil, false
			}
			// Uppercase names
			row[1] = strings.ToUpper(row[1])
			return row, true
		}),
	)
	writer.Write(os.Stdout)
}

Custom Headers

writer := tocsv.New(rows,
    tocsv.WithCustomHeader([]string{"User ID", "Full Name", "Email Address"}),
    tocsv.WithHeader(true),
)

Configuration Options

Performance

• The library is optimized for efficient memory usage:
• Processes data in streaming fashion
• Minimal allocations during conversion
• Batched CSV writing

License

MIT - See LICENSE for details.